START-INFO-DIR-ENTRY * mysql: (mysql). *MySQL* documentation. END-INFO-DIR-ENTRY Table of Contents ***************** General Information About MySQL MySQL, MySQL AB, and Open Source What Is MySQL What Is MySQL AB About This Manual Conventions Used in This Manual History of MySQL The Main Features of MySQL How Stable Is MySQL? How Big Can MySQL Tables Be? Year 2000 Compliance MySQL Information Sources Books About MySQL General SQL Information and Tutorials Useful MySQL-related Links MySQL Mailing Lists The MySQL Mailing Lists Asking Questions or Reporting Bugs How to Report Bugs or Problems Guidelines for Answering Question on the Mailing List MySQL Licensing and Support MySQL Licensing Policy Copyrights Used by MySQL Copyright Changes Example Licensing Situations Selling Products that use MySQL ISP MySQL Services Running a Web Server Using MySQL MySQL Licensing and Support Costs Payment information Contact Information Types of Commercial Support Basic E-mail Support Extended E-mail Support Login Support Extended Login Support Telephone Support Support for other table handlers How Standards-compatible Is MySQL? MySQL Extensions to ANSI SQL92 MySQL Differences Compared to ANSI SQL92 Running MySQL in ANSI Mode Functionality Missing from MySQL Sub-selects `SELECT INTO TABLE' Transactions Stored Procedures and Triggers Foreign Keys Reasons NOT to Use Foreign Keys constraints Views `--' as the Start of a Comment What Standards Does MySQL Follow? How to Cope Without `COMMIT'/`ROLLBACK' Known errors and design deficiencies in MySQL How MySQL Compares to Other Databases How MySQL Compares to `mSQL' How to Convert `mSQL' Tools for MySQL How `mSQL' and MySQL Client/Server Communications Protocols Differ How `mSQL' 2.0 SQL Syntax Differs from MySQL How MySQL Compares to PostgreSQL MySQL and PostgreSQL development strategies Featurewise Comparison of MySQL and PostgreSQL Benchmarking MySQL and PostgreSQL MySQL and the future (The TODO) Things that should be in 4.0 Things that must be done in the real near future Things that have to be done sometime Some things we don't have any plans to do MySQL Installation Quick Standard Installation of MySQL Installing MySQL on Linux Installing MySQL on Windows General Installation Issues How to Get MySQL Operating Systems Supported by MySQL Which MySQL Version to Use Installation Layouts How and When Updates Are Released MySQL Binaries Compiled by MySQL AB Installing a MySQL Source Distribution Quick Installation Overview Applying Patches Typical `configure' Options Installing from the Development Source Tree Problems Compiling? MIT-pthreads Notes Post-installation Setup and Testing Problems Running `mysql_install_db' Problems Starting the MySQL Server Starting and Stopping MySQL Automatically Upgrading/Downgrading MySQL Upgrading From Version 3.22 to Version 3.23 Upgrading from Version 3.21 to Version 3.22 Upgrading from Version 3.20 to Version 3.21 Upgrading to Another Architecture Operating System Specific Notes Linux Notes (All Linux Versions) Linux Notes for Binary Distributions Linux x86 Notes Linux SPARC Notes Linux Alpha Notes Linux PowerPC Notes Linux MIPS Notes Linux IA64 Notes Windows Notes Starting MySQL on Windows 95 or Windows 98 Starting MySQL on Windows NT or Windows 2000 Running MySQL on Windows Connecting to a Remote MySQL from Windows with SSH Splitting Data Across Different Disks on Windows Compiling MySQL Clients on Windows MySQL-Windows Compared to Unix MySQL Solaris Notes Solaris 2.7/2.8 Notes Solaris x86 Notes BSD Notes FreeBSD Notes NetBSD notes OpenBSD Notes OpenBSD 2.5 Notes OpenBSD 2.8 Notes BSD/OS Notes BSD/OS Version 2.x Notes BSD/OS Version 3.x Notes BSD/OS Version 4.x Notes Mac OS X Notes Mac OS X Public Beta Mac OS X Server Other Unix Notes HP-UX Notes for Binary Distributions HP-UX Version 10.20 Notes HP-UX Version 11.x Notes IBM-AIX notes SunOS 4 Notes Alpha-DEC-UNIX Notes (Tru64) Alpha-DEC-OSF1 Notes SGI Irix Notes SCO Notes SCO Unixware Version 7.0 Notes OS/2 Notes BeOS Notes Novell Netware Notes Introduction to MySQL: A MySQL Tutorial Connecting to and Disconnecting from the Server Entering Queries Creating and Using a Database Creating and Selecting a Database Creating a Table Loading Data into a Table Retrieving Information from a Table Selecting All Data Selecting Particular Rows Selecting Particular Columns Sorting Rows Date Calculations Working with `NULL' Values Pattern Matching Counting Rows Using More Than one Table Getting Information About Databases and Tables Examples of Common Queries The Maximum Value for a Column The Row Holding the Maximum of a Certain Column Maximum of Column per Group The Rows Holding the Group-wise Maximum of a Certain Field Using user variables Using Foreign Keys Searching on Two Keys Calculating visits per day Using `mysql' in Batch Mode Queries from Twin Project Find all Non-distributed Twins Show a Table on Twin Pair Status Using MySQL with Apache MySQL Database Administration Configuring MySQL mysqld Command-line Options my.cnf Option Files Installing Many Servers on the Same Machine Running Multiple MySQL Servers on the Same Machine General Security Issues and the MySQL Access Privilege System General Security Guidelines How to Make MySQL Secure Against Crackers Startup Options for `mysqld' Concerning Security What the Privilege System Does How the Privilege System Works Privileges Provided by MySQL Connecting to the MySQL Server Access Control, Stage 1: Connection Verification Access Control, Stage 2: Request Verification Causes of `Access denied' Errors MySQL User Account Management `GRANT' and `REVOKE' Syntax MySQL User Names and Passwords When Privilege Changes Take Effect Setting Up the Initial MySQL Privileges Adding New Users to MySQL Setting Up Passwords Keeping Your Password Secure Disaster Prevention and Recovery Database Backups `BACKUP TABLE' Syntax `RESTORE TABLE' Syntax `CHECK TABLE' Syntax `REPAIR TABLE' Syntax Using `myisamchk' for Table Maintenance and Crash Recovery `myisamchk' Invocation Syntax General Options for `myisamchk' Check Options for `myisamchk' Repair Options for myisamchk Other Options for `myisamchk' `myisamchk' Memory Usage Using `myisamchk' for Crash Recovery How to Check Tables for Errors How to Repair Tables Table Optimization Setting Up a Table Maintenance Regimen Getting Information About a Table Database Administration Language Reference `OPTIMIZE TABLE' Syntax `ANALYZE TABLE' Syntax `FLUSH' Syntax `KILL' Syntax `SHOW' Syntax Retrieving information about Database, Tables, Columns, and Indexes `SHOW TABLE STATUS' `SHOW STATUS' `SHOW VARIABLES' `SHOW LOGS' `SHOW PROCESSLIST' `SHOW GRANTS' `SHOW CREATE TABLE' MySQL Localization and International Usage The Character Set Used for Data and Sorting Non-English Error Messages Adding a New Character Set The character definition arrays String Collating Support Multi-byte Character Support MySQL Server-Side Scripts and Utilities Overview of the Server-Side Scripts and Utilities safe_mysqld, the wrapper around mysqld mysqld_multi, program for managing multiple *MySQL* servers myisampack, The MySQL Compressed Read-only Table Generator mysqld-max, An extended mysqld server MySQL Client-Side Scripts and Utilities Overview of the Client-Side Scripts and Utilities The Command-line Tool mysqladmin, Administrating a MySQL Server Using `mysqlcheck' for Table Maintenance and Crash Recovery mysqldump, Dumping Table Structure and Data mysqlhotcopy, Copying MySQL Databases and Tables mysqlimport, Importing Data from Text Files Showing Databases, Tables, and Columns perror, Explaining Error Codes How to Run SQL Commands from a Text File The MySQL Log Files The Error Log The General Query Log The Update Log The Binary Update Log The Slow Query Log Log File Maintenance Replication in MySQL Introduction Replication Implementation Overview How To Set Up Replication Replication Features and Known Problems Replication Options in my.cnf SQL Commands Related to Replication Replication FAQ Troubleshooting Replication MySQL Optimization Optimization Overview MySQL Design Limitations/Tradeoffs Portability What Have We Used MySQL For? The MySQL Benchmark Suite Using Your Own Benchmarks Optimizing `SELECT's and Other Queries `EXPLAIN' Syntax (Get Information About a `SELECT') Estimating Query Performance Speed of `SELECT' Queries How MySQL Optimizes `WHERE' Clauses How MySQL Optimizes `DISTINCT' How MySQL Optimizes `LEFT JOIN' and `RIGHT JOIN' How MySQL Optimizes `LIMIT' Speed of `INSERT' Queries Speed of `UPDATE' Queries Speed of `DELETE' Queries Other Optimization Tips Locking Issues How MySQL Locks Tables Table Locking Issues Optimizing Database Structure Design Choices Get Your Data as Small as Possible How MySQL Uses Indexes Column Indexes Multiple-Column Indexes How MySQL Opens and Closes Tables Drawbacks to Creating Large Numbers of Tables in the Same Database Why So Many Open tables? Optimizing the MySQL Server System/Compile Time and Startup Parameter Tuning Tuning Server Parameters How Compiling and Linking Affects the Speed of MySQL How MySQL Uses Memory How MySQL uses DNS `SET' Syntax Disk Issues Using Symbolic Links Using Symbolic Links for Databases Using Symbolic Links for Tables MySQL Language Reference Language Structure Literals: How to Write Strings and Numbers Strings Numbers Hexadecimal Values `NULL' Values Database, Table, Index, Column, and Alias Names Case Sensitivity in Names User Variables Comment Syntax Is MySQL Picky About Reserved Words? Column Types Numeric Types Date and Time Types Y2K Issues and Date Types The `DATETIME', `DATE', and `TIMESTAMP' Types The `TIME' Type The `YEAR' Type String Types The `CHAR' and `VARCHAR' Types The `BLOB' and `TEXT' Types The `ENUM' Type The `SET' Type Choosing the Right Type for a Column Using Column Types from Other Database Engines Column Type Storage Requirements Functions for Use in `SELECT' and `WHERE' Clauses Non-Type-Specific Operators and Functions Parenthesis Comparison Operators Logical Operators Control Flow Functions String Functions String Comparison Functions Case Sensitivity Numeric Functions Arithmetic Operations Mathematical Functions Date and Time Functions Other Functions Bit Functions Miscellaneous Functions Data Manipulation: `SELECT', `INSERT', `UPDATE', `DELETE' `SELECT' Syntax `JOIN' Syntax `INSERT' Syntax `INSERT ... SELECT' Syntax `INSERT DELAYED' syntax `UPDATE' Syntax `DELETE' Syntax `TRUNCATE' Syntax `REPLACE' Syntax `LOAD DATA INFILE' Syntax Data Definition: `CREATE', `DROP', `ALTER' `CREATE DATABASE' Syntax `DROP DATABASE' Syntax `CREATE TABLE' Syntax Silent Column Specification Changes `ALTER TABLE' Syntax `RENAME TABLE' Syntax `DROP TABLE' Syntax `CREATE INDEX' Syntax `DROP INDEX' Syntax Basic MySQL User Utility Commands `USE' Syntax `DESCRIBE' Syntax (Get Information About Columns) MySQL Transactional and Locking Commands `BEGIN/COMMIT/ROLLBACK' Syntax `LOCK TABLES/UNLOCK TABLES' Syntax `SET TRANSACTION' Syntax MySQL Full-text Search Fulltext restrictions Fine-tuning MySQL Full-text Search New Features of Full-text Search to Appear in MySQL 4.0 Full-text Search TODO MySQL Table Types MyISAM Tables Space Needed for Keys MyISAM Table Formats Static (Fixed-length) Table Characteristics Dynamic Table Characteristics Compressed Table Characteristics MyISAM table problems. Corrupted MyISAM tables. Clients is using or hasn't closed the table properly MERGE Tables ISAM Tables HEAP Tables BDB or Berkeley_DB Tables Overview of BDB Tables Installing BDB BDB startup options Some characteristic of `BDB' tables: Some things we need to fix for BDB in the near future: Operating systems supported by *BDB* Errors You May Get When Using BDB Tables InnoDB Tables InnoDB tables overview InnoDB startup options Creating InnoDB table space If something goes wrong in database creation Creating InnoDB tables Converting MyISAM tables to InnoDB Adding and removing InnoDB data and log files Backing up and recovering an InnoDB database Checkpoints Moving an InnoDB database to another machine InnoDB transaction model Consistent read Locking reads Next-key locking: avoiding the phantom problem Locks set by different SQL statements in InnoDB Deadlock detection and rollback Performance tuning tips Implementation of multiversioning Table and index structures Physical structure of an index Insert buffering Adaptive hash indexes Physical record structure How an auto-increment column works in InnoDB File space management and disk i/o Disk i/o File space management Defragmenting a table Error handling Some restrictions on InnoDB tables InnoDB contact information MySQL APIs MySQL PHP API Common Problems with MySQL and PHP MySQL Perl API `DBI' with `DBD::mysql' The `DBI' Interface More `DBI'/`DBD' Information MySQL ODBC Support How To Install MyODBC How to Fill in the Various Fields in the ODBC Administrator Program Connect parameters for MyODBC How to Report Problems with MyODBC Programs Known to Work with MyODBC How to Get the Value of an `AUTO_INCREMENT' Column in ODBC Reporting Problems with MyODBC MySQL C API C API Datatypes C API Function Overview C API Function Descriptions `mysql_affected_rows()' `mysql_close()' `mysql_connect()' `mysql_change_user()' `mysql_character_set_name()' `mysql_create_db()' `mysql_data_seek()' `mysql_debug()' `mysql_drop_db()' `mysql_dump_debug_info()' `mysql_eof()' `mysql_errno()' `mysql_error()' `mysql_escape_string()' `mysql_fetch_field()' `mysql_fetch_fields()' `mysql_fetch_field_direct()' `mysql_fetch_lengths()' `mysql_fetch_row()' `mysql_field_count()' `mysql_field_seek()' `mysql_field_tell()' `mysql_free_result()' `mysql_get_client_info()' `mysql_get_host_info()' `mysql_get_proto_info()' `mysql_get_server_info()' `mysql_info()' `mysql_init()' `mysql_insert_id()' `mysql_kill()' `mysql_list_dbs()' `mysql_list_fields()' `mysql_list_processes()' `mysql_list_tables()' `mysql_num_fields()' `mysql_num_rows()' `mysql_options()' `mysql_ping()' `mysql_query()' `mysql_real_connect()' `mysql_real_escape_string()' `mysql_real_query()' `mysql_reload()' `mysql_row_seek()' `mysql_row_tell()' `mysql_select_db()' `mysql_shutdown()' `mysql_stat()' `mysql_store_result()' `mysql_thread_id()' `mysql_use_result()' Common questions and problems when using the C API Why Is It that After `mysql_query()' Returns Success, `mysql_store_result()' Sometimes Returns `NULL?' What Results Can I Get From a Query? How Can I Get the Unique ID for the Last Inserted Row? Problems Linking with the C API Building Client Programs How to Make a Thread-safe Client MySQL C++ APIs Borland C++ MySQL Java Connectivity (JDBC) MySQL Python APIs MySQL Tcl APIs MySQL Eiffel wrapper Extending MySQL Adding New Functions to MySQL `CREATE FUNCTION/DROP FUNCTION' Syntax Adding a New User-definable Function UDF Calling Sequences Argument Processing Return Values and Error Handling Compiling and Installing User-definable Functions Adding a New Native Function Adding New Procedures to MySQL Procedure Analyse Writing a Procedure MySQL Internals MySQL Threads MySQL Test Suite Running the MySQL Test Suite Extending the MySQL Test Suite Reporting Bugs in the MySQL Test Suite Problems and Common Errors How to Determine What Is Causing Problems What to Do if MySQL Keeps Crashing Problems When Linking with the MySQL Client Library Some Common Errors When Using MySQL `Access denied' Error `MySQL server has gone away' Error `Can't connect to [local] MySQL server' error `Host '...' is blocked' Error `Too many connections' Error `Some non-transactional changed tables couldn't be rolled back' Error `Out of memory' Error `Packet too large' Error Communication Errors / Aborted Connection `The table is full' Error `Can't create/write to file' Error `Commands out of sync' Error in Client `Ignoring user' Error `Table 'xxx' doesn't exist' Error `Cant' initialize character set xxx' error. How MySQL Handles a Full Disk Where MySQL Stores Temporary Files How to Protect `/tmp/mysql.sock' from Being Deleted How to Run MySQL As a Normal User How to Reset a Forgotten Password Problems with File Permissions File Not Found Problems Using `DATE' Columns Time Zone Problems Case Sensitivity in Searches Problems with `NULL' Values Problems with `alias' Deleting Rows from Related Tables Solving Problems with No Matching Rows Problems with `ALTER TABLE'. How To Change the Order of Columns in a Table TEMPORARY TABLE problems Environment Variables Some MySQL Users General News Sites Some Web Search Engines Some Information Search Engines Concentrated on Some Area Online Magazines Web Sites that Use MySQL as a Backend Some Domain/Internet/Web and Related Services Web Sites that Use `PHP' and MySQL Some MySQL Consultants Programming Uncategorized Pages MySQL customer usage Contributed Programs APIs Clients Web Tools Performance Benchmarking Tools Authentication Tools Converters Using MySQL with Other Products Useful Tools RPMs for Common Tools (Most Are for RedHat 6.1) Useful Functions Windows programs Uncategorized Credits Developers at MySQL AB Contributors to MySQL Supporters to MySQL MySQL change history Changes in release 4.0.x (Development; Alpha) Changes in release 4.0.0 Changes in release 3.23.x (Stable) Changes in release 3.23.41 Changes in release 3.23.40 Changes in release 3.23.39 Changes in release 3.23.38 Changes in release 3.23.37 Changes in release 3.23.36 Changes in release 3.23.35 Changes in release 3.23.34a Changes in release 3.23.34 Changes in release 3.23.33 Changes in release 3.23.32 Changes in release 3.23.31 Changes in release 3.23.30 Changes in release 3.23.29 Changes in release 3.23.28 Changes in release 3.23.27 Changes in release 3.23.26 Changes in release 3.23.25 Changes in release 3.23.24 Changes in release 3.23.23 Changes in release 3.23.22 Changes in release 3.23.21 Changes in release 3.23.20 Changes in release 3.23.19 Changes in release 3.23.18 Changes in release 3.23.17 Changes in release 3.23.16 Changes in release 3.23.15 Changes in release 3.23.14 Changes in release 3.23.13 Changes in release 3.23.12 Changes in release 3.23.11 Changes in release 3.23.10 Changes in release 3.23.9 Changes in release 3.23.8 Changes in release 3.23.7 Changes in release 3.23.6 Changes in release 3.23.5 Changes in release 3.23.4 Changes in release 3.23.3 Changes in release 3.23.2 Changes in release 3.23.1 Changes in release 3.23.0 Changes in release 3.22.x (Older; Still supported) Changes in release 3.22.35 Changes in release 3.22.34 Changes in release 3.22.33 Changes in release 3.22.32 Changes in release 3.22.31 Changes in release 3.22.30 Changes in release 3.22.29 Changes in release 3.22.28 Changes in release 3.22.27 Changes in release 3.22.26 Changes in release 3.22.25 Changes in release 3.22.24 Changes in release 3.22.23 Changes in release 3.22.22 Changes in release 3.22.21 Changes in release 3.22.20 Changes in release 3.22.19 Changes in release 3.22.18 Changes in release 3.22.17 Changes in release 3.22.16 Changes in release 3.22.15 Changes in release 3.22.14 Changes in release 3.22.13 Changes in release 3.22.12 Changes in release 3.22.11 Changes in release 3.22.10 Changes in release 3.22.9 Changes in release 3.22.8 Changes in release 3.22.7 Changes in release 3.22.6 Changes in release 3.22.5 Changes in release 3.22.4 Changes in release 3.22.3 Changes in release 3.22.2 Changes in release 3.22.1 Changes in release 3.22.0 Changes in release 3.21.x Changes in release 3.21.33 Changes in release 3.21.32 Changes in release 3.21.31 Changes in release 3.21.30 Changes in release 3.21.29 Changes in release 3.21.28 Changes in release 3.21.27 Changes in release 3.21.26 Changes in release 3.21.25 Changes in release 3.21.24 Changes in release 3.21.23 Changes in release 3.21.22 Changes in release 3.21.21a Changes in release 3.21.21 Changes in release 3.21.20 Changes in release 3.21.19 Changes in release 3.21.18 Changes in release 3.21.17 Changes in release 3.21.16 Changes in release 3.21.15 Changes in release 3.21.14b Changes in release 3.21.14a Changes in release 3.21.13 Changes in release 3.21.12 Changes in release 3.21.11 Changes in release 3.21.10 Changes in release 3.21.9 Changes in release 3.21.8 Changes in release 3.21.7 Changes in release 3.21.6 Changes in release 3.21.5 Changes in release 3.21.4 Changes in release 3.21.3 Changes in release 3.21.2 Changes in release 3.21.0 Changes in release 3.20.x Changes in release 3.20.18 Changes in release 3.20.17 Changes in release 3.20.16 Changes in release 3.20.15 Changes in release 3.20.14 Changes in release 3.20.13 Changes in release 3.20.11 Changes in release 3.20.10 Changes in release 3.20.9 Changes in release 3.20.8 Changes in release 3.20.7 Changes in release 3.20.6 Changes in release 3.20.3 Changes in release 3.20.0 Changes in release 3.19.x Changes in release 3.19.5 Changes in release 3.19.4 Changes in release 3.19.3 Comments on porting to other systems Debugging a MySQL server Compiling MYSQL for debugging. Creating trace files Debugging mysqld under gdb Using a stack trace Using log files to find cause of errors in mysqld Making a test case when you experience table corruption Debugging a MySQL client The DBUG package. Locking methods Comments about RTS threads Differences between different thread packages Description of MySQL regular expression syntax What is Unireg? GNU GENERAL PUBLIC LICENSE Preamble How to Apply These Terms to Your New Programs GNU LESSER GENERAL PUBLIC LICENSE Preamble How to Apply These Terms to Your New Libraries Pieces of the manual in transit Installing a MySQL Binary Distribution Perl Installation Comments Installing Perl on Unix Installing ActiveState Perl on Windows Installing the MySQL Perl Distribution on Windows Problems Using the Perl `DBI'/`DBD' Interface Functions for Use with `GROUP BY' Clauses SQL command, type and function index Concept Index This is a manual for *MySQL*. This version is about the 3.23.41 version of *MySQL*. You can find a manual about any older version of *MySQL* in the binary or source distribution for that version. General Information About MySQL ******************************* This is the *MySQL* reference manual; it documents *MySQL* Version 3.23.41. As *MySQL* is work in progress, the manual gets updated frequently. There is a very good chance that this version is out of date, unless you are looking at it online. The most recent version of this manual is available at `http://www.mysql.com/documentation/' in many different formats. If you have a hard time finding information in the manual, you can try the searchable PHP version at `http://www.mysql.com/documentation/manual.php'. *MySQL* is a very fast, multi-threaded, multi-user, and robust SQL (Structured Query Language) database server. *MySQL* is free software. It is licensed with the *GNU GENERAL PUBLIC LICENSE* `http://www.gnu.org/'. *Note Licensing and Support::. The *MySQL* home page (http://www.mysql.com/) provides the latest information about *MySQL*. The following list describes some useful sections of the manual: * For information about the company behind *MySQL*, see *Note What is MySQL AB::. * For a discussion of *MySQL*'s capabilities, see *Note Features::. * For installation instructions, see *Note Installing::. * For tips on porting *MySQL* to new architectures or operating systems, see *Note Porting::. * For information about upgrading from a Version 3.22 release, see *Note Upgrading-from-3.22::. * For a tutorial introduction to *MySQL*, see *Note Tutorial::. * For examples of SQL and benchmarking information, see the benchmarking directory (`sql-bench' in the distribution). * For a history of new features and bug fixes, see *Note News::. * For a list of currently known bugs and misfeatures, see *Note Bugs::. * For future plans, see *Note TODO::. * For a list of all the contributors to this project, see *Note Credits::. *IMPORTANT:* Reports of errors (often called bugs), as well as questions and comments, should be sent to the mailing list at . *Note Bug reports::. The `mysqlbug' script should be used to generate bug reports. For source distributions, the `mysqlbug' script can be found in the `scripts' directory. For binary distributions, `mysqlbug' can be found in the `bin' directory. If you have found a sensitive security bug in *MySQL*, you should send an email to . If you have any suggestions concerning additions or corrections to this manual, please send them to the manual team at . This is a reference manual; it does not provide general instruction on SQL or relational database concepts. If you want general information about SQL, see *Note General-SQL::. For books that focus more specifically on *MySQL*, see *Note MySQL-Books::. MySQL, MySQL AB, and Open Source ================================ What Is MySQL ------------- *MySQL*, the most popular Open Source SQL database, is provided by *MySQL AB*. *MySQL AB* is a commercial company that builds its business providing services around the *MySQL* database. *Note What is MySQL AB::. *MySQL* is a database management system. A database is a structured collection of data. It may be anything from a simple shopping list to a picture gallery or the vast amounts of information in a corporate network. To add, access, and process data stored in a computer database, you need a database management system such as *MySQL*. Since computers are very good at handling large amounts of data, database management plays a central role in computing, as stand-alone utilities, or as parts of other applications. *MySQL* is a relational database management system. A relational database stores data in separate tables rather than putting all the data in one big storeroom. This adds speed and flexibility. The tables are linked by defined relations making it possible to combine data from several tables on request. The SQL part of *MySQL* stands for "Structured Query Language" - the most common standardized language used to access databases. *MySQL* is Open Source Software. Open Source means that it is possible for anyone to use and modify. Anybody can download *MySQL* from the Internet and use it without paying anything. Anybody so inclined can study the source code and change it to fit their needs. *MySQL* uses the GPL (GNU General Public License) `http://www.gnu.org', to define what you may and may not do with the software in different situations. If you feel uncomfortable with the GPL or need to embed *MySQL* into a commercial application you can buy a commercially licensed version from us. Why use *MySQL*? *MySQL* is very fast, reliable, and easy to use. If that is what you are looking for, you should give it a try. *MySQL* also has a very practical set of features developed in very close cooperation with our users. You can find a performance comparison of *MySQL* to some other database managers on our benchmark page. *Note MySQL Benchmarks::. *MySQL* was originally developed to handle very large databases much faster than existing solutions and has been successfully used in highly demanding production environments for several years. Though under constant development, *MySQL* today offers a rich and very useful set of functions. The connectivity, speed, and security make *MySQL* highly suited for accessing databases on the Internet. The technical features of *MySQL* For advanced technical information, see *Note Reference::. *MySQL* is a client/server system that consists of a multi-threaded SQL server that supports different backends, several different client programs and libraries, administrative tools, and several programming interfaces. We also provide *MySQL* as a multi-threaded library which you can link into your application to get a smaller, faster, easier to manage product. *MySQL* has a lot of contributed software available. It is very likely that you will find that your favorite application or language already supports *MySQL*. The official way to pronounce *MySQL* is "My Ess Que Ell" (not MY-SEQUEL). But we try to avoid correcting people who say MY-SEQUEL. What Is MySQL AB ---------------- *MySQL AB* is the Swedish company owned and run by the *MySQL* founders and main developers. We are dedicated to developing *MySQL* and spreading our database to new users. *MySQL AB* owns the copyright to the *MySQL* server source code and the *MySQL* trademark. A significant amount of revenues from our services goes to developing *MySQL*. *Note What-is::. *MySQL AB* has been profitable providing *MySQL* from the start. We don't get any outside funding, but have earned all our money ourselves. We are searching after partners that would like to support our development of *MySQL* so that we could accelerate the development pace. If you are interested in doing this, you can email about this! *MySQL AB* has currently 20+ people (`http://www.mysql.com/development/team.html') on its payroll and is growing rapidly. Our main sources of income are: * Commercial high quality support for *MySQL* provided by the *MySQL* developers themselves. If you are interested in purchasing a support contract, please visit `https://order.mysql.com/' to view our support options or to order support. * Consulting services. We have developers and consultants in 12 countries and partners in many other countries that can help you with almost any *MySQL* related issues. If you need consulting services, please email a good description of your needs to ! If we can't handle this ourselves we can usually find a partner or a developer that can help you with your problems. * We sell licenses for using *MySQL* as an embedded database. *Note Cost::. If you have a commercial product for which you need a fast, high quality database, but you can't afford to make your product Open Source, you can buy the right to use the *MySQL* server under a normal commercial copyright. If you are interested in this you can buy *MySQL* licenses at `https://order.mysql.com/' or contact us at . * Advertising. `http://www.mysql.com/' is a very popular web site with more than 10,000,000 page views per months (January 2001). By putting a banner on this you are guaranteed to reach a lot of potential customers in the Open source, Linux and database community. If you are interested in this email . * We are building a partner program to be able to provide *MySQL* services in every country. If you are interested in becoming a partner of *MySQL AB* please visit `http://www.mysql.com/information/partners.html' or email . * We provide *MySQL* training through our partner programs. For more information, please email . * The *MySQL* brand has, since 1995, been associated with speed and reliability, and is known to be something you can depend upon. If you are interested in using the *MySQL* trademark in your marketing, you can email about this. The *MySQL* core values show our dedication to *MySQL* and Open Source. We want *MySQL* to be: * The best and the most used database in the world. * Available and affordable for all. * Easy to use. * Continuously improved while remaining fast and safe. * Fun to use and improve. * Free from bugs. *MySQL AB* and the people of *MySQL AB*: * Promote Open Source Philosophy and support the Open Source Community. * Aim to be good citizens. * Prefer partners that share our values and mind-set. * Answer mail and give support. * Are a virtual company, networking with others. * Work against software patents. About This Manual ----------------- This manual is currently available in Texinfo, plain text, Info, HTML, PostScript, and PDF versions. The primary document is the Texinfo file. The HTML version is produced automatically using a modified version of `texi2html'. The plain text and Info versions are produced with `makeinfo'. The Postscript version is produced using `texi2dvi' and `dvips'. The PDF version is produced with `pdftex'. This manual is written and maintained by David Axmark, Michael (Monty) Widenius, Jeremy Cole, and Paul DuBois. For other contributors, see *Note Credits::. Conventions Used in This Manual ------------------------------- This manual uses certain typographical conventions: `constant' Constant-width font is used for command names and options; SQL statements; database, table and column names; C and Perl code; and environment variables. Example: "To see how `mysqladmin' works, invoke it with the `--help' option." `filename' Constant-width font with surrounding quotes is used for filenames and pathnames. Example: "The distribution is installed under the `/usr/local/' directory." `c' Constant-width font with surrounding quotes is also used to indicate character sequences. Example: "To specify a wild card, use the `%' character." _italic_ Italic font is used for emphasis, _like this_. *boldface* Boldface font is used for access privilege names (for example, "do not grant the *process* privilege lightly") and occasionally to convey *especially strong emphasis*. When commands are shown that are meant to be executed by a particular program, the program is indicated by a prompt shown before the command. For example, `shell>' indicates a command that you execute from your login shell, and `mysql>' indicates a command that you execute from the `mysql' client program: shell> type a shell command here mysql> type a mysql command here Shell commands are shown using Bourne shell syntax. If you are using a `csh'-style shell, you may need to issue commands slightly differently. For example, the sequence to set an environment variable and run a command looks like this in Bourne shell syntax: shell> VARNAME=value some_command For `csh', you would execute the sequence like this: shell> setenv VARNAME value shell> some_command Often, database, table, and column names must be substituted into commands. To indicate that such substitution is necessary, this manual uses `db_name', `tbl_name' and `col_name'. For example, you might see a statement like this: mysql> SELECT col_name FROM db_name.tbl_name; This means that if you were to enter a similar statement, you would supply your own database, table, and column names, perhaps like this: mysql> SELECT author_name FROM biblio_db.author_list; SQL statements may be written in uppercase or lowercase. When this manual shows a SQL statement, uppercase is used for particular keywords if those keywords are under discussion (to emphasize them) and lowercase is used for the rest of the statement. For example, you might see the following in a discussion of the `SELECT' statement: mysql> SELECT count(*) FROM tbl_name; On the other hand, in a discussion of the `COUNT()' function, the same statement would be written like this: mysql> select COUNT(*) from tbl_name; If no particular emphasis is intended, all keywords are written uniformly in uppercase. In syntax descriptions, square brackets (`[' and `]') are used to indicate optional words or clauses: DROP TABLE [IF EXISTS] tbl_name When a syntax element consists of a number of alternatives, the alternatives are separated by vertical bars (`|'). When one member from a set of choices *may* be chosen, the alternatives are listed within square brackets (`[' and `]'): TRIM([[BOTH | LEADING | TRAILING] [remstr] FROM] str) When one member from a set of choices *must* be chosen, the alternatives are listed within braces (`{' and `}'): {DESCRIBE | DESC} tbl_name {col_name | wild} History of MySQL ---------------- We once started out with the intention of using `mSQL' to connect to our tables using our own fast low-level (ISAM) routines. However, after some testing we came to the conclusion that `mSQL' was not fast enough nor flexible enough for our needs. This resulted in a new SQL interface to our database but with almost the same API interface as `mSQL'. This API was chosen to ease porting of third-party code. The derivation of the name *MySQL* is not perfectly clear. Our base directory and a large number of our libraries and tools have had the prefix "my" for well over 10 years. However, Monty's daughter (some years younger) is also named My. Which of the two gave its name to *MySQL* is still a mystery, even for us. The Main Features of MySQL -------------------------- The following list describes some of the important characteristics of *MySQL*: * Fully multi-threaded using kernel threads. This means it can easily use multiple CPUs if available. * C, C++, Eiffel, Java, Perl, PHP, Python and Tcl APIs. *Note Clients::. * Works on many different platforms. *Note Which OS::. * Many column types: signed/unsigned integers 1, 2, 3, 4, and 8 bytes long, `FLOAT', `DOUBLE', `CHAR', `VARCHAR', `TEXT', `BLOB', `DATE', `TIME', `DATETIME', `TIMESTAMP', `YEAR', `SET', and `ENUM' types. *Note Column types::. * Very fast joins using an optimized one-sweep multi-join. * Full operator and function support in the `SELECT' and `WHERE' parts of queries. For example: mysql> SELECT CONCAT(first_name, " ", last_name) FROM tbl_name WHERE income/dependents > 10000 AND age > 30; * SQL functions are implemented through a highly optimized class library and should be as fast as possible! Usually there isn't any memory allocation at all after query initialization. * Full support for SQL `GROUP BY' and `ORDER BY' clauses. Support for group functions (`COUNT()', `COUNT(DISTINCT ...)', `AVG()', `STD()', `SUM()', `MAX()' and `MIN()'). * Support for `LEFT OUTER JOIN' and `RIGHT OUTER JOIN' with ANSI SQL and ODBC syntax. * You can mix tables from different databases in the same query (as of Version 3.22). * A privilege and password system that is very flexible and secure, and allows host-based verification. Passwords are secure because all password traffic is encrypted when you connect to a server. * ODBC (Open-DataBase-Connectivity) support for Win32 (with source). All ODBC 2.5 functions and many others. For example, you can use MS Access to connect to your *MySQL* server. *Note ODBC::. * Very fast B-tree disk tables with index compression. * Up to 32 indexes per table are allowed. Each index may consist of 1 to 16 columns or parts of columns. The maximum index length is 500 bytes (this may be changed when compiling *MySQL*). An index may use a prefix of a `CHAR' or `VARCHAR' field. * Fixed-length and variable-length records. * In-memory hash tables which are used as temporary tables. * Handles large databases. We are using *MySQL* with some databases that contain 50,000,000 records and we know of users that uses *MySQL* with 60,000 tables and about 5,000,000,000 rows * All columns have default values. You can use `INSERT' to insert a subset of a table's columns; those columns that are not explicitly given values are set to their default values. * Uses GNU Automake, Autoconf, and Libtool for portability. * Written in C and C++. Tested with a broad range of different compilers. * A very fast thread-based memory allocation system. * No memory leaks. *MySQL* has been tested with Purify, a commercial memory leakage detector. * Includes `myisamchk', a very fast utility for table checking, optimization, and repair. All of the functionality of `myisamchk' is also available through the SQL interface as well. *Note MySQL Database Administration::. * Full support for several different character sets, including ISO-8859-1 (Latin1), big5, ujis, and more. For example, the Scandinavian characters `a*', `a"' and `o"' are allowed in table and column names. * All data are saved in the chosen character set. All comparisons for normal string columns are case insensitive. * Sorting is done according to the chosen character set (the Swedish way by default). It is possible to change this when the *MySQL* server is started up. To see an example of very advanced sorting, look at the Czech sorting code. *MySQL* supports many different character sets that can be specified at compile and run time. * Aliases on tables and columns are allowed as in the SQL92 standard. * `DELETE', `INSERT', `REPLACE', and `UPDATE' return the number of rows that were changed (affected). It is possible to return the number of rows matched instead by setting a flag when connecting to the server. * Function names do not clash with table or column names. For example, `ABS' is a valid column name. The only restriction is that for a function call, no spaces are allowed between the function name and the `(' that follows it. *Note Reserved words::. * All *MySQL* programs can be invoked with the `--help' or `-?' options to obtain online assistance. * The server can provide error messages to clients in many languages. *Note Languages::. * Clients may connect to the *MySQL* server using TCP/IP Sockets, Unix Sockets (Unix), or Named Pipes (NT). * The *MySQL*-specific `SHOW' command can be used to retrieve information about databases, tables, and indexes. The `EXPLAIN' command can be used to determine how the optimizer resolves a query. How Stable Is MySQL? -------------------- This section addresses the questions "How stable is *MySQL*?" and "Can I depend on *MySQL* in this project?" We will try to clarify some issues and to answer some of the more important questions that seem to concern many people. This section has been put together from information gathered from the mailing list (which is very active in reporting bugs). At TcX, *MySQL* has worked without any problems in our projects since mid-1996. When *MySQL* was released to a wider public, we noticed that there were some pieces of "untested code" that were quickly found by the new users who made queries in a manner different than our own. Each new release has had fewer portability problems than the previous one (even though each has had many new features). Each release of *MySQL* has been usable, and there have been problems only when users start to use code from the "gray zones." Naturally, outside users don't know what the gray zones are; this section attempts to indicate those that are currently known. The descriptions deal with Version 3.23 of *MySQL*. All known and reported bugs are fixed in the latest version, with the exception of the bugs listed in the bugs section, which are things that are design-related. *Note Bugs::. *MySQL* is written in multiple layers and different independent modules. These modules are listed below with an indication of how well-tested each of them is: *The ISAM table handler -- Stable* This manages storage and retrieval of all data in *MySQL* Version 3.22 and earlier. In all *MySQL* releases there hasn't been a single (reported) bug in this code. The only known way to get a corrupted table is to kill the server in the middle of an update. Even that is unlikely to destroy any data beyond rescue, because all data are flushed to disk between each query. There hasn't been a single bug report about lost data because of bugs in *MySQL*. *The MyISAM table handler -- Stable* This is new in *MySQL* Version 3.23. It's largely based on the ISAM table code but has a lot of new and very useful features. *The parser and lexical analyser -- Stable* There hasn't been a single reported bug in this system for a long time. *The C client code -- Stable* No known problems. In early Version 3.20 releases, there were some limitations in the send/receive buffer size. As of Version 3.21, the buffer size is now dynamic up to a default of 16M. *Standard client programs -- Stable* These include `mysql', `mysqladmin', `mysqlshow', `mysqldump', and `mysqlimport'. *Basic SQL -- Stable* The basic SQL function system and string classes and dynamic memory handling. Not a single reported bug in this system. *Query optimizer -- Stable* *Range optimizer -- Stable* *Join optimizer -- Stable* *Locking -- Gamma* This is very system-dependent. On some systems there are big problems using standard OS locking (`fcntl()'). In these cases, you should run the *MySQL* daemon with the `--skip-locking' flag. Problems are known to occur on some Linux systems, and on SunOS when using NFS-mounted file systems. *Linux threads -- Stable* The major problem found has been with the `fcntl()' call, which is fixed by using the `--skip-locking' option to `mysqld'. Some people have reported lockup problems with Version 0.5. LinuxThreads will need to be recompiled if you plan to use 1000+ concurrent connections. Although it is possible to run that many connections with the default LinuxThreads (however, you will never go above 1021), the default stack spacing of 2 MB makes the application unstable, and we have been able to reproduce a coredump after creating 1021 idle connections. *Note Linux::. *Solaris 2.5+ pthreads -- Stable* We use this for all our production work. *MIT-pthreads (Other systems) -- Stable* There have been no reported bugs since Version 3.20.15 and no known bugs since Version 3.20.16. On some systems, there is a "misfeature" where some operations are quite slow (a 1/20 second sleep is done between each query). Of course, MIT-pthreads may slow down everything a bit, but index-based `SELECT' statements are usually done in one time frame so there shouldn't be a mutex locking/thread juggling. *Other thread implementions -- Beta - Gamma* The ports to other systems are still very new and may have bugs, possibly in *MySQL*, but most often in the thread implementation itself. *`LOAD DATA ...', `INSERT ... SELECT' -- Stable* Some people thought they had found bugs here, but these usually have turned out to be misunderstandings. Please check the manual before reporting problems! *`ALTER TABLE' -- Stable* Small changes in Version 3.22.12. *DBD -- Stable* Now maintained by Jochen Wiedmann (). Thanks! *`mysqlaccess' -- Stable* Written and maintained by Yves Carlier (). Thanks! *`GRANT' -- Stable* Big changes made in *MySQL* Version 3.22.12. **MyODBC* (uses ODBC SDK 2.5) -- Gamma* It seems to work well with some programs. *Replication - Beta / Gamma* We are still working on replication, so don't expect this to be rock solid yet. On the other hand, some *MySQL* users are already using this with good results. *BDB Tables - Beta* The Berkeley DB code is very stable, but we are still improving the interface between *MySQL* and BDB tables, so it will take some time before this is as tested as the other table types. *InnoDB Tables - Beta* This is a recent addition to `MySQL'. They appear to work good and can be used after some initial testing. *Automatic recovery of MyISAM tables - Beta* This only affects the new code that checks if the table was closed properly on open and executes an automatic check/repair of the table if it wasn't. *MERGE tables - Beta / Gamma* The usage of keys on `MERGE' tables is still not that tested. The other part of the `MERGE' code is quite well tested. *FULLTEXT - Beta* Text search seems to work, but is still not widely used. *MySQL AB* provides e-mail support for paying customers, but the *MySQL* mailing list usually provides answers to common questions. Bugs are usually fixed right away with a patch; for serious bugs, there is almost always a new release. How Big Can MySQL Tables Be? ---------------------------- *MySQL* Version 3.22 has a 4G limit on table size. With the new `MyISAM' in *MySQL* Version 3.23 the maximum table size is pushed up to 8 million terabytes (2 ^ 63 bytes). Note, however, that operating systems have their own file size limits. Here are some examples: *Operating System* *File Size Limit* Linux-Intel 32 bit 2G, 4G or more, depends on Linux version Linux-Alpha 8T (?) Solaris 2.5.1 2G (possible 4G with patch) Solaris 2.6 4G Solaris 2.7 Intel 4G Solaris 2.7 ULTRA-SPARC 8T (?) On Linux 2.2 you can get bigger tables than 2G by using the LFS patch for the ext2 file system. On Linux 2.4 there exists also patches for ReiserFS to get support for big files. This means that the table size for *MySQL* is normally limited by the operating system. By default, *MySQL* tables have a maximum size of about 4G. You can check the maximum table size for a table with the `SHOW TABLE STATUS' command or with the `myisamchk -dv table_name'. *Note SHOW::. If you need bigger tables than 4G (and your operating system supports this), you should set the `AVG_ROW_LENGTH' and `MAX_ROWS' parameter when you create your table. *Note CREATE TABLE::. You can also set these later with `ALTER TABLE'. *Note ALTER TABLE::. If your big table is going to be read-only, you could use `myisampack' to merge and compress many tables to one. `myisampack' usually compresses a table by at least 50%, so you can have, in effect, much bigger tables. *Note `myisampack': myisampack. You can go around the operating system file limit for `MyISAM' data files by using the `RAID' option. *Note CREATE TABLE::. Another solution can be the included MERGE library, which allows you to handle a collection of identical tables as one. *Note MERGE tables: MERGE. Year 2000 Compliance -------------------- *MySQL* itself has no problems with Year 2000 (Y2K) compliance: * *MySQL* uses Unix time functions and has no problems with dates until `2069'; all 2-digit years are regarded to be in the range `1970' to `2069', which means that if you store `01' in a `year' column, *MySQL* treats it as `2001'. * All *MySQL* date functions are stored in one file `sql/time.cc' and coded very carefully to be year 2000-safe. * In *MySQL* Version 3.22 and later, the new `YEAR' column type can store years `0' and `1901' to `2155' in 1 byte and display them using 2 or 4 digits. You may run into problems with applications that use *MySQL* in a way that is not Y2K-safe. For example, many old applications store or manipulate years using 2-digit values (which are ambiguous) rather than 4-digit values. This problem may be compounded by applications that use values such as `00' or `99' as "missing" value indicators. Unfortunately, these problems may be difficult to fix, because different applications may be written by different programmers, each of whom may use a different set of conventions and date-handling functions. Here is a simple demonstration illustrating that *MySQL* doesn't have any problems with dates until the year 2030: mysql> DROP TABLE IF EXISTS y2k; Query OK, 0 rows affected (0.01 sec) mysql> CREATE TABLE y2k (date date, date_time datetime, time_stamp timestamp); Query OK, 0 rows affected (0.00 sec) mysql> INSERT INTO y2k VALUES -> ("1998-12-31","1998-12-31 23:59:59",19981231235959), -> ("1999-01-01","1999-01-01 00:00:00",19990101000000), -> ("1999-09-09","1999-09-09 23:59:59",19990909235959), -> ("2000-01-01","2000-01-01 00:00:00",20000101000000), -> ("2000-02-28","2000-02-28 00:00:00",20000228000000), -> ("2000-02-29","2000-02-29 00:00:00",20000229000000), -> ("2000-03-01","2000-03-01 00:00:00",20000301000000), -> ("2000-12-31","2000-12-31 23:59:59",20001231235959), -> ("2001-01-01","2001-01-01 00:00:00",20010101000000), -> ("2004-12-31","2004-12-31 23:59:59",20041231235959), -> ("2005-01-01","2005-01-01 00:00:00",20050101000000), -> ("2030-01-01","2030-01-01 00:00:00",20300101000000), -> ("2050-01-01","2050-01-01 00:00:00",20500101000000); Query OK, 13 rows affected (0.01 sec) Records: 13 Duplicates: 0 Warnings: 0 mysql> SELECT * FROM y2k; +------------+---------------------+----------------+ | date | date_time | time_stamp | +------------+---------------------+----------------+ | 1998-12-31 | 1998-12-31 23:59:59 | 19981231235959 | | 1999-01-01 | 1999-01-01 00:00:00 | 19990101000000 | | 1999-09-09 | 1999-09-09 23:59:59 | 19990909235959 | | 2000-01-01 | 2000-01-01 00:00:00 | 20000101000000 | | 2000-02-28 | 2000-02-28 00:00:00 | 20000228000000 | | 2000-02-29 | 2000-02-29 00:00:00 | 20000229000000 | | 2000-03-01 | 2000-03-01 00:00:00 | 20000301000000 | | 2000-12-31 | 2000-12-31 23:59:59 | 20001231235959 | | 2001-01-01 | 2001-01-01 00:00:00 | 20010101000000 | | 2004-12-31 | 2004-12-31 23:59:59 | 20041231235959 | | 2005-01-01 | 2005-01-01 00:00:00 | 20050101000000 | | 2030-01-01 | 2030-01-01 00:00:00 | 20300101000000 | | 2050-01-01 | 2050-01-01 00:00:00 | 00000000000000 | +------------+---------------------+----------------+ 13 rows in set (0.00 sec) This shows that the `DATE' and `DATETIME' types will not give any problems with future dates (they handle dates until the year 9999). The `TIMESTAMP' type, which is used to store the current time, has a range up to only `2030-01-01'. `TIMESTAMP' has a range of `1970' to `2030' on 32-bit machines (signed value). On 64-bit machines it handles times up to `2106' (unsigned value). Even though *MySQL* is Y2K-compliant, it is your responsibility to provide unambiguous input. See *Note Y2K issues:: for *MySQL*'s rules for dealing with ambiguous date input data (data containing 2-digit year values). MySQL Information Sources ========================= Books About MySQL ----------------- While this manual is still the right place for up to date technical information, its primary goal is to contain everything there is to know about *MySQL*. It is sometimes nice to have a bound book to read in bed or while you travel. Here is a list of books about *MySQL* and related subjects (in English). By purchasing a book through these hyperlinks provided herein, you are contributing to the development of *MySQL*. _MySQL_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0735709211&bfmtype=book) Publisher New Riders Author Paul DuBois Pub Date 1st Edition December 1999 ISBN 0735709211 Pages 800 Price $49.99 US Downloadable examples `samp_db' distribution (http://www.kitebird.com/mysql-book/) Errata are available here (http://www.kitebird.com/mysql-book/errata.html) Foreword by Michael "Monty" Widenius, *MySQL* Moderator. In _MySQL_, Paul DuBois provides you with a comprehensive guide to one of the most popular relational database systems. Paul has contributed to the online documentation for *MySQL* and is an active member of the *MySQL* community. The principal *MySQL* developer, Monty Widenius, and a network of his fellow developers reviewed the manuscript, and provided Paul with the kind of insight no one else could supply. Instead of merely giving you a general overview of *MySQL*, Paul teaches you how to make the most of its capabilities. Through two sample database applications that run throughout the book, he gives you solutions to problems you're sure to face. He helps you integrate *MySQL* efficiently with third-party tools, such as PHP and Perl, enabling you to generate dynamic Web pages through database queries. He teaches you to write programs that access *MySQL* databases, and also provides a comprehensive set of references to column types, operators, functions, SQL syntax, *MySQL* programming, C API, Perl `DBI', and PHP API. _MySQL_ simply gives you the kind of information you won't find anywhere else. If you use *MySQL*, this book provides you with: * An introduction to *MySQL* and SQL. * Coverage of *MySQL*'s data types and how to use them. * Thorough treatment of how to write client programs in C. * A guide to using the Perl `DBI' and PHP APIs for developing command-line and Web-based applications. * Tips on administrative issues such as user accounts, backup, crash recovery, and security. * Help in choosing an ISP for *MySQL* access. * A comprehensive reference for *MySQL*'s data types, operators, functions, and SQL statements and utilities. * Complete reference guides for *MySQL*'s C API, the Perl `DBI' API, and PHP's *MySQL*-related functions. _MySQL & mSQL_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=1565924347&bfmtype=book) Publisher O'Reilly Authors Randy Jay Yarger, George Reese & Tim King Pub Date 1st Edition July 1999 ISBN 1-56592-434-7, Order Number: 4347 Pages 506 Price $34.95 This book teaches you how to use *MySQL* and `mSQL', two popular and robust database products that support key subsets of SQL on both Linux and Unix systems. Anyone who knows basic C, Java, Perl, or Python can write a program to interact with a database, either as a stand-alone application or through a Web page. This book takes you through the whole process, from installation and configuration to programming interfaces and basic administration. Includes plenty of tutorial material. _Sams' Teach Yourself MySQL in 21 Days_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0672319144&bfmtype=book) Publisher Sams Authors Mark Maslakowski and Tony Butcher Pub Date June 2000 ISBN 0672319144 Pages 650 Price $39.99 Sams' _Teach Yourself MySQL in 21 Days_ is for intermediate Linux users who want to move into databases. A large share of the audience is Web developers who need a database to store large amounts of information that can be retrieved via the Web. Sams' _Teach Yourself MySQL in 21 Days_ is a practical, step-by-step tutorial. The reader will learn to design and employ this open source database technology into his or her Web site using practical, hands-on examples to follow. _E-Commerce Solutions with MySQL_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0761524452&bfmtype=book) Publisher Prima Communications, Inc. Authors N/A Pub Date January 2000 ISBN 0761524452 Pages 500 Price $39.99 No description available. _MySQL and PHP from Scratch_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0789724405&bfmtype=book) Publisher Que Authors N/A Pub Date September 2000 ISBN 0789724405 Pages 550 Price $34.99 This book puts together information on installing, setting up, and troubleshooting Apache, *MySQL*, PHP3, and IMP into one complete volume. You also learn how each piece is part of a whole by learning, step-by-step, how to create a web-based e-mail system. Learn to run the equivalent of Active Server Pages (ASP) using PHP3, set up an e-commerce site using a database and the Apache web server, and create a data entry system (such as sales, product quality tracking, customer preferences, etc) that no installation in the PC. _Professional MySQL Programming_ Available Barnes and Noble (http://shop.barnesandnoble.com/bookSearch/isbnInquiry.asp?isbn=1861005164) Publisher Wrox Press, Inc. Authors N/A Pub Date Late 2001 ISBN 1861005164 Pages 1000 Price $49.99 No description available. _Professional Linux Programming_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=1861003013&bfmtype=book) Publisher Wrox Press, Inc. Authors N/A Pub Date September 2000 ISBN 1861003013 Pages 1155 Price $47.99 In this follow-up to the best-selling _Beginning Linux Programming_, you will learn from the authors' real-world knowledge and experience of developing software for Linux; you'll be taken through the development of a sample 'DVD Store' application, with 'theme' chapters addressing different aspects of its implementation. Meanwhile, individual "take-a-break" chapters cover important topics that go beyond the bounds of the central theme. All focus on the practical aspects of programming, showing how crucial it is to choose the right tools for the job, use them as they should be used, and get things right first time. _PHP and MySQL Web Development_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0672317842&bfmtype=book) Publisher Sams Authors Luke Welling, Laura Thomson Pub Date March 2001 ISBN 0672317842 Pages 700 Price $49.99 _PHP and MySQL Web Development_ introduces you to the advantages of implementing both *MySQL* and PHP. These advantages are detailed through the provision of both statistics and several case studies. A practical web application is developed throughout the book, providing you with the tools necessary to implement a functional online database. Each function is developed separately, allowing you the choice to incorporate only those parts that you would like to implement. Programming concepts of the PHP language are highlighted, including functions which tie *MySQL* support into a PHP script and advanced topics regarding table manipulation. *Books recommended by the MySQL Developers* _SQL-99 Complete, Really_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0879305681&bfmtype=book) Publisher CMP Books Authors Peter Gulutzan, Trudy Pelzer Pub Date April 1999 ISBN 0879305681 Pages 1104 Price $55.96 This book contains complete descriptions of the new standards for syntax, data structures, and retrieval processes of SQL databases. As an example-based reference manual, it includes all of the CLI functions, information, schema tables, and status codes, as well as a working SQL database provided on the companion disk. _C, A reference manual_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0133262243&bfmtype=book) Publisher Prentice Hall Authors Samuel P. Harbison, Guy L. Steele Pub Date September 1994 ISBN 0133262243 Pages 480 Price $35.99 A new and improved revision of the bestselling C language reference. This manual introduces the notion of "Clean C", writing C code that can be compiled as a C++ program, C programming style that emphasizes correctness, portability, maintainability, and incorporates the ISO C Amendment 1 (1994) which specifies new facilities for writing portable, international programs in C. _C++ for Real Programmers_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0120499428&bfmtype=book) Publisher Academic Press, Incorporated Authors Jeff Alger, Jim Keogh Pub Date February 1998 ISBN 0120499428 Pages 388 Price $39.95 _C++ For Real Programmers_ bridges the gap between C++ as described in beginner and intermediate-level books and C++ as it is practiced by experts. Numerous valuable techniques are described, organized into three simple themes: indirection, class hierarchies, and memory management. It also provides in-depth coverage of template creation, exception handling, pointers and optimization techniques. The focus of the book is on ANSI C++ and, as such, is compiler independent. _C++ For Real Programmers_ is a revision of _Secrets of the C++ Masters_ and includes a new appendix comparing C++ with Java. The book comes with a 3.5" disk for Windows with source code. _Algorithms in C_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0201514257&bfmtype=book) Publisher Addison Wesley Longman, Inc. Authors Robert Sedgewick Pub Date April 1990 ISBN 0201514257 Pages 648 Price $45.75 _Algorithms in C_ describes a variety of algorithms in a number of areas of interest, including: sorting, searching, string-processing, and geometric, graph and mathematical algorithms. The book emphasizes fundamental techniques, providing readers with the tools to confidently implement, run, and debug useful algorithms. _Multithreaded Programming with Pthreads_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0136807291&bfmtype=book) Publisher Prentice Hall Authors Bil Lewis, Daniel J. Berg Pub Date October 1997 ISBN 0136807291 Pages 432 Price $34.95 Based on the best-selling _Threads Primer_, _Multithreaded Programming with Pthreads_ gives you a solid understanding of Posix threads: what they are, how they work, when to use them, and how to optimize them. It retains the clarity and humor of _Threads Primer_, but includes expanded comparisons to Win32 and OS/2 implementations. Code examples tested on all of the major UNIX platforms are featured along with detailed explanations of how and why they use threads. _Programming the PERL DBI: Database Programming with PERL_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=1565926994&bfmtype=book) Publisher O'Reilly & Associates, Incorporated Authors Alligator Descartes, Tim Bunce Pub Date February 2000 ISBN 1565926994 Pages 400 Price $27.96 _Programming the Perl DBI_ is coauthored by Alligator Descartes, one of the most active members of the DBI community, and by Tim Bunce, the inventor of DBI. For the uninitiated, the book explains the architecture of DBI and shows you how to write DBI-based programs. For the experienced DBI dabbler, this book explains DBI's nuances and the peculiarities of each individual DBD. The book includes: * An introduction to DBI and its design. * How to construct queries and bind parameters. * Working with database, driver, and statement handles. * Debugging techniques. * Coverage of each existing DBD. * A complete reference to DBI. General SQL Information and Tutorials ------------------------------------- The following book has been recommended by several people on the *MySQL* mailing list: Judith S. Bowman, Sandra L. Emerson and Marcy Darnovsky _The Practical SQL Handbook: Using Structured Query Language_ Second Edition Addison-Wesley ISBN 0-201-62623-3 http://www.awl.com The following book has also received some recommendations by *MySQL* users: Martin Gruber _Understanding SQL_ ISBN 0-89588-644-8 Publisher Sybex 510 523 8233 Alameda, CA USA A SQL tutorial is available on the net at http://w3.one.net/~jhoffman/sqltut.htm Useful MySQL-related Links -------------------------- Apart from the following links, you can find and download a lot of *MySQL* programs, tools and APIs from the Contrib directory (http://www.mysql.com/Downloads/Contrib/). *MySQL* Tutorials and Manuals --------------------- MySQL Myths Debunked (http://netgraft.com/~mbac/research/mysqlmyths.html) *MySQL* used in the real world. `http://www.4t2.com/mysql' Information about the German MySQL mailing list. `http://www2.rent-a-database.de/mysql/' *MySQL* handbook in German. `http://www.bitmover.com:8888//home/bk/mysql' Web access to the *MySQL* BitKeeper repository. `http://www.analysisandsolutions.com/code/mybasic.htm' Beginners *MySQL* Tutorial on how to install and set up *MySQL* on a Windows machine. `http://www.devshed.com/Server_Side/MySQL/' A lot of *MySQL* tutorials. `http://mysql.hitstar.com/' MySQL manual in Chinese. `http://www.linuxplanet.com/linuxplanet/tutorials/1046/1/' Setting Up a *MySQL*-based Web site. `http://www.hotwired.com/webmonkey/backend/tutorials/tutorial1.html' *MySQL*-Perl tutorial. `http://www.iserver.com/support/contrib/perl5/modules.html' Installing new Perl modules that require locally installed modules. `http://www.hotwired.com/webmonkey/databases/tutorials/tutorial4.html' PHP/*MySQL* Tutorial. `http://www.useractive.com/' Hands on tutorial for *MySQL*. Porting MySQL/Using MySQL on Different Systems ---------------------------------------------- `http://xclave.macnn.com/MySQL/' The Mac OS Xclave. Running *MySQL* on Mac OS X. `http://www.prnet.de/RegEx/mysql.html' MySQL for Mac OS X Server. `http://www.latencyzero.com/macosx/mysql.html' Building MySQL for Mac OS X. `http://www.essencesw.com/Software/mysqllib.html' New Client libraries for the Mac OS Classic (Macintosh). `http://www.lilback.com/macsql/' Client libraries for Mac OS Classic (Macintosh). `http://sixk.maniasys.com/index_en.html' MySQL for Amiga Perl-related Links ------------------ `http://dbimysql.photoflux.com/' Perl DBI with *MySQL* FAQ. MySQL Discussion Forums ----------------------- `http://www.weberdev.com/' Examples using *MySQL*; (check Top 20) `http://futurerealm.com/forum/futureforum.htm' FutureForum Web Discussion Software. Commercial Applications that Support MySQL ------------------------------------------ `http://www.supportwizard.com/' SupportWizard; Interactive helpdesk on the Web (This product includes a licensed copy of *MySQL*.) `http://www.sonork.com/' Sonork, Instant Messenger that is not only Internet oriented. It's focused on private networks and on small to medium companies. Client is free, server is free for up to 5 seats. `http://www.stweb.org/' StWeb - Stratos Web and Application server - An easy-to-use, cross platform, Internet/Intranet development and deployment system for development of web-enabled applications. The standard version of StWeb has a native interface to *MySQL* database. `http://www.rightnowtech.com/' Right Now Web; Web automation for customer service. `http://www.icaap.org/Bazaar/' Bazaar; Interactive Discussion Forums with Web interface. `http://www.phonesweep.com/' PhoneSweepT is the world's first commercial Telephone Scanner. Many break-ins in recent years have come not through the Internet, but through unauthorized dial-up modems. PhoneSweep lets you find these modems by repeatedly placing phone calls to every phone number that your organization controls. PhoneSweep has a built-in expert system that can recognize more than 250 different kinds of remote-access programs, including Carbon Copy(TM), pcANYWHERE(TM), and Windows NT RAS. All information is stored in the SQL database. It then generates a comprehensive report detailing which services were discovered on which dial-up numbers in your organization. SQL Clients and Report Writers ------------------------------ urSQL (http://www.urbanresearch.com/software/utils/urbsql/index.html) SQL Editor and Query Utility. Custom syntax highlighting, editable results grid, exportable result-sets, basic *MySQL* admin functions, Etc.. For Windows. MySQL Data Manager (http://www.edatanew.com/) *MySQL* Data Manager * is platform independent web client (written in perl) for *MySQL* server over TCP/IP. `http://ksql.sourceforge.net/' KDE *MySQL* client. `http://www.ecker-software.de' A Windows GUI client by David Ecker. `http://www.icaap.org/software/kiosk/' Kiosk; a *MySQL* client for database management. Written in Perl. Will be a part of Bazaar. `http://www.casestudio.com/' Db design tool that supports MySQL 3.23. `http://home.skif.net/~voland/zeos/eng/index.html' Zeos - A client that supports *MySQL*, Interbase and PostgreSQL. `http://www.geocities.com/SiliconValley/Ridge/4280/GenericReportWriter/grwhome.html' A free report writer in Java `http://www.javaframework.de' MySQLExport - Export of *MySQL* create statements and data in a lot of different formats (SQL, HTML, CVS, text, ZIP, GZIP...) `http://dlabs.4t2.com' M2D, a *MySQL* Administration client for Windows. M2D supports administration of *MySQL* databases, creation of new databases and tables, editing, and more. `http://dlabs.4t2.com' Dexter, a small server written in Perl which can be used as a proxy server for *MySQL* or as a database extender. `http://www.scibit.com/Products/Software/Utils/Mascon.asp' Mascon is a powerful Win32 GUI for administering MySQL databases. `http://www.rtlabs.com/' MacSQL Monitor. GUI for MySQL, ODBC, and JDBC databases for the Mac OS. Distributions that Include MySQL -------------------------------- `http://www.suse.com/' SuSE Linux (6.1 and above) `http://www.redhat.com/' RedHat Linux (7.0 and above) `http://distro.conectiva.com.br' Conectiva Linux (4.0 and above) Web Development Tools that Support *MySQL* ------------------------------------------ `http://www.php.net/' PHP: A server-side HTML-embedded scripting language. `http://www.midgard-project.org' The Midgard Application Server; a powerful Web development environment based on *MySQL* and PHP. `http://www.smartworker.org' SmartWorker is a platform for Web application development. `http://xsp.lentus.se/' XSP: e(X)tendible (S)erver (P)ages and is a HTML embedded tag language written in Java (previously known as XTAGS.) `http://www.dbServ.de/' dbServ is an extension to a web server to integrate database output into your HTML code. You may use any HTML function in your output. Only the client will stop you. It works as standalone server or as Java servlet. `http://www.chilisoft.com/' Platform independent ASP from Chili!Soft `http://www.voicenet.com/~zellert/tjFM' A JDBC driver for *MySQL*. `http://www.wernhart.priv.at/php/' *MySQL* + PHP demos. `http://www.dbwww.com/' ForwardSQL: HTML interface to manipulate *MySQL* databases. `http://www.daa.com.au/~james/www-sql/' WWW-SQL: Display database information. `http://www.minivend.com/minivend/' Minivend: A Web shopping cart. `http://www.heitml.com/' HeiTML: A server-side extension of HTML and a 4GL language at the same time. `http://www.metahtml.com/' Metahtml: A Dynamic Programming Language for WWW Applications. `http://www.binevolve.com/' VelocityGen for Perl and Tcl. `http://hawkeye.net/' Hawkeye Internet Server Suite. `http://www.fastflow.com/' Network Database Connection For Linux `http://www.wdbi.net/' WDBI: Web browser as a universal front end to databases which supports *MySQL* well. `http://www.webgroove.com/' WebGroove Script: HTML compiler and server-side scripting language. `http://www.ihtml.com/' A server-side Web site scripting language. `ftp://ftp.igc.apc.org/pub/myodbc/README' How to use *MySQL* with ColdFusion on Solaris. `http://calistra.com/MySQL/' Calistra's ODBC *MySQL* Administrator. `http://www.webmerger.com' Webmerger - This CGI tool interprets files and generates dynamic output based on a set of simple tags. Ready-to-run drivers for *MySQL* and PostgreSQL through ODBC. `http://phpclub.net/' PHPclub - Tips and tricks for PHP. `http://www.penguinservices.com/scripts' *MySQL* and Perl Scripts. `http://www.widgetchuck.com' The Widgetchuck; Web Site Tools and Gadgets `http://www.adcycle.com/' AdCycle - advertising management software. `http://sourceforge.net/projects/pwpage/' pwPage - provides an extremely fast and simple approach to the creation of database forms. That is, if a database table exists and an HTML page has been constructed using a few simple guidelines, pwPage can be immediately used for table data selections, insertions, updates, deletions and selectable table content reviewing. `http://www.omnis-software.com/products/studio/studio.html' OMNIS Studio is a rapid application development (RAD) tool. `http://www.webplus.com' talentsoft Web+ 4.6 - a powerful and comprehensive development language for use in creating web-based client/server applications without writing complicated, low-level, and time-consuming CGI programs. Database Design Tools with MySQL Support ---------------------------------------- `http://www.mysql.com/documentation/dezign/' "DeZign for databases" is a database development tool that uses an entity relationship diagram (ERD). Web Servers with *MySQL* Tools ------------------------------ `ftp://ftp.kcilink.com/pub/' mod_auth_mysql, An Apache authentication module. `http://www.roxen.com/' The Roxen Challenger Web server. Extensions for Other Programs ----------------------------- `http://www.seawood.org/msql_bind/' *MySQL* support for BIND (The Internet Domain Name Server). `http://www.inet-interactive.com/sendmail/' *MySQL* support for Sendmail and Procmail. Using *MySQL* with Other Programs --------------------------------- `http://www.iserver.com/support/addonhelp/database/mysql/msaccess.html' Using *MySQL* with Access. `http://www.iserver.com/support/contrib/perl5/modules.html' Installing new Perl modules that require locally installed modules. ODBC-related Links ------------------ `http://www.iodbc.org/' Popular iODBC Driver Manager (libiodbc) now available as Open Source. `http://users.ids.net/~bjepson/freeODBC/' The FreeODBC Pages. `http://genix.net/unixODBC/' The unixODBC Project goals are to develop and promote unixODBC to be the definitive standard for ODBC on the Linux platform. This is to include GUI support for KDE. `http://www.sw-soft.com/products/BtrieveODBC/' A *MySQL*-based ODBC driver for Btrieve. *API*-related Links ------------------- `http://www.jppp.com/' Partially implemented TDataset-compatible components for *MySQL*. `http://www.riverstyx.net/qpopmysql/' qpopmysql - A patch to allow POP3 authentication from a *MySQL* database. There's also a link to Paul Khavkine's patch for Procmail to allow any MTA to deliver to users in a *MySQL* database. `http://www.pbc.ottawa.on.ca' Visual Basic class generator for Active X. `http://www.essencesw.com/Software/mysqllib.html' New Client libraries for the Mac OS Classic (Macintosh). `http://www.lilback.com/macsql/' Client libraries for the Macintosh. `http://www.essencesw.com/Plugins/mysqlplug.html' Plugin for REALbasic (for Macintosh) `http://www.iis.ee.ethz.ch/~neeri/macintosh/gusi-qa.html' A library that emulates BSD sockets and pthreads on Macintosh. This can be used if you want to compile the *MySQL* client library on Mac. It could probably even be sued to port *MySQL* to Macintosh, but we don't know of anyone that has tried that. `http://www.dedecker.net/jessie/scmdb/' SCMDB - an add-on for SCM that ports the *MySQL* C library to scheme (SCM). With this library scheme developers can make connections to a *MySQL* database and use embedded SQL in their programs. Other *MySQL*-related Links --------------------------- SAT (http://www.satisoft.com/) The Small Application Toolkit (SAT) is a collection of utilities intended to simplify the development of small, multi-user, GUI based applications in a (Microsoft -or- X) Windows Client / Unix Server environment. `http://www.wix.com/mysql-hosting/' Registry of Web providers who support *MySQL*. `http://www.softagency.co.jp/mysql/index.en.html' Links about using *MySQL* in Japan/Asia. `http://abattoir.cc.ndsu.nodak.edu/~nem/mysql/udf/' *MySQL* UDF Registry. `http://www.open.com.au/products.html' Commercial Web defect tracking system. `http://www.stonekeep.com/pts/' PTS: Project Tracking System. `http://tomato.nvgc.vt.edu/~hroberts/mot' Job and software tracking system. `http://www.cynergi.net/exportsql/' ExportSQL: A script to export data from Access95+. `http://SAL.KachinaTech.COM/H/1/MYSQL.html' SAL (Scientific Applications on Linux) *MySQL* entry. `http://www.infotech-nj.com/itech/index.shtml' A consulting company which mentions *MySQL* in the right company. `http://www.pmpcs.com/' PMP Computer Solutions. Database developers using *MySQL* and `mSQL'. `http://www.aewa.org/' Airborne Early Warning Association. `http://www.dedserius.com/y2kmatrix/' Y2K tester. SQL and Database Interfaces --------------------------- `http://java.sun.com/products/jdbc/' The JDBC database access API. `http://www.gagme.com/mysql' Patch for `mSQL' Tcl. `http://www.amsoft.ru/easysql/' EasySQL: An ODBC-like driver manager. `http://www.lightlink.com/hessling/rexxsql.html' A REXX interface to SQL databases. `http://www.mytcl.cx/' Tcl interface based on tcl-sql with many bugfixes. `http://www.binevolve.com/~tdarugar/tcl-sql/' Tcl interface. `http://www.contrib.andrew.cmu.edu/~shadow/sql.html' SQL Reference Page with a lot of interesting links. Examples of MySQL Use --------------------- `http://www.little6.com/about/linux/' Little6 Inc., An online contract and job finding site that is powered by *MySQL*, PHP3, and Linux. `http://www.delec.com/is/products/prep/examples/BookShelf/index.html' DELECis - A tool that makes it very easy to create an automatically generated table documentation. They have used *MySQL* as an example. `http://www.worldrecords.com' World Records - A search engine for information about music that uses *MySQL* and PHP. `http://www.webtechniques.com/archives/1998/01/note/' A Contact Database using *MySQL* and PHP. `http://modems.rosenet.net/mysql/' Web based interface and Community Calendar with PHP. `http://www.odbsoft.com/cook/sources.htm' Perl package to generate html from a SQL table structure and for generating SQL statements from an html form. `http://www.gusnet.cx/proj/telsql/' Basic telephone database using `DBI'/`DBD'. `http://tecfa.unige.ch/guides/java/staf2x/ex/jdbc/coffee-break' JDBC examples by Daniel K. Schneider. `http://www.spade.com/linux/howto/PostgreSQL-HOWTO-41.html' SQL BNF `http://www.ooc.com/' Object Oriented Concepts Inc; CORBA applications with examples in source. `http://www.pbc.ottawa.on.ca/' DBWiz; Includes an example of how to manage cursors in VB. `http://keilor.cs.umass.edu/pluribus/' Pluribus is a free search engine that learns to improve the quality of its results over time. Pluribus works by recording which pages a user prefers among those returned for a query. A user votes for a page by selecting it; Pluribus then uses that knowledge to improve the quality of the results when someone else submits the same (or similar) query. Uses PHP and *MySQL*. `http://www.stopbit.com/' Stopbit - A technology news site using *MySQL* and PHP. `http://www.linuxsupportline.com/~kalendar/' KDE based calendar manager - The calendar manager has both single user (file based) and multi-user (*MySQL* database) support. `http://tim.desert.net/~tim/imger/' Example of storing/retrieving images with *MySQL* and CGI. `http://www.penguinservices.com/scripts' Online shopping cart system. `http://www.city-gallery.com/album/' Old Photo Album - The album is a collaborative popular history of photography project that generates all pages from data stored in a *MySQL* database. Pages are dynamically generated through a php3 interface to the database content. Users contribute images and descriptions. Contributed images are stored on the web server to avoid storing them in the database as BLOBs. All other information is stored on the shared *MySQL* server. General Database Links ---------------------- `http://www.pcslink.com/~ej/dbweb.html' Database Jump Site `http://black.hole-in-the.net/guy/webdb/' Homepage of the webdb-l (Web Databases) mailing list. `http://www.symbolstone.org/technology/perl/DBI/index.html' Perl `DBI'/`DBD' modules homepage. `http://www.student.uni-koeln.de/cygwin/' Cygwin tools. Unix on top of Windows. `http://dbasecentral.com/' dbasecentral.com; Development and distribution of powerful and easy-to-use database applications and systems. `http://www.tek-tips.com/' Tek-Tips Forums are 800+ independent peer-to-peer non-commercial support forums for Computer Professionals. Features include automatic e-mail notification of responses, a links library, and member confidentiality guaranteed. `http://www.public.asu.edu/~peterjn/btree/' B-Trees: Balanced Tree Data Structures. `http://www.fit.qut.edu.au/~maire/baobab/lecture/sld001.htm' A lecture about B-Trees. There are also many Web pages that use *MySQL*. *Note Users::. Send any additions to this list to . We now require that you show a *MySQL* logo somewhere if you wish your site to be added. It is okay to have it on a "used tools" page or something similar. MySQL Mailing Lists ------------------- This section introduces you to the *MySQL* mailing lists, and gives some guidelines as to how to use them. The MySQL Mailing Lists ....................... To subscribe to the main *MySQL* mailing list, send a message to the electronic mail address . To unsubscribe from the main *MySQL* mailing list, send a message to the electronic mail address . Only the address to which you send your messages is significant. The subject line and the body of the message are ignored. If your reply address is not valid, you can specify your address explicitly. Adding a hyphen to the subscribe or unsubscribe command word, followed by your address with the `@' character in your address replaced by a `='. For example, to subscribe `your_name@host.domain', send a message to `mysql-subscribe-your_name=host.domain@lists.mysql.com'. Mail to or is handled automatically by the ezmlm mailing list processor. Information about ezmlm is available at The ezmlm Website (http://www.ezmlm.org). To post a message to the list itself, send your message to `mysql@lists.mysql.com'. However, please _do not_ send mail about subscribing or unsubscribing to , because any mail sent to that address is distributed automatically to thousands of other users. Your local site may have many subscribers to . If so, it may have a local mailing list, so that messages sent from `lists.mysql.com' to your site are propagated to the local list. In such cases, please contact your system administrator to be added to or dropped from the local *MySQL* list. If you wish to have traffic for a mailing list go to a separate mailbox in your mail program, set up a filter based on the message headers. You can use either the `List-ID:' or `Delivered-To:' headers to identify list messages. The following *MySQL* mailing lists exist: ` announce' This is for announcement of new versions of *MySQL* and related programs. This is a low volume list all *MySQL* users should subscribe to. ` mysql' The main list for general *MySQL* discussion. Please note that some topics are better discussed on the more-specialized lists. If you post to the wrong list, you may not get an answer! ` mysql-digest' The `mysql' list in digest form. That means you get all individual messages, sent as one large mail message once a day. ` bugs' On this list you should only post a full, repeatable bug report using the `mysqlbug' script (if you are running on Windows, you should include a description of the operating system and the *MySQL* version). Preferably, you should test the problem using the latest stable or development version of *MySQL* before posting! Anyone should be able to repeat the bug by just using `mysql test < script' on the included test case. All bugs posted on this list will be corrected or documented in the next *MySQL* release! If there are only small code changes involved, we will also post a patch that fixes the problem. ` bugs-digest' The `bugs' list in digest form. ` internals' A list for people who work on the *MySQL* code. On this list one can also discuss *MySQL* development and post patches. ` internals-digest' A digest version of the `internals' list. ` java' Discussion about *MySQL* and Java. Mostly about the JDBC drivers. ` java-digest' A digest version of the `java' list. ` win32' All things concerning *MySQL* on Microsoft operating systems such as Win95, Win98, NT, and Win2000. ` win32-digest' A digest version of the `win32' list. ` myodbc' All things about connecting to *MySQL* with ODBC. ` myodbc-digest' A digest version of the `myodbc' list. ` plusplus' All things concerning programming with the C++ API to *MySQL*. ` plusplus-digest' A digest version of the `plusplus' list. ` msql-mysql-modules' A list about the Perl support in *MySQL*. msql-mysql-modules ` msql-mysql-modules-digest' A digest version of the `msql-mysql-modules' list. You subscribe or unsubscribe to all lists in the same way as described above. In your subscribe or unsubscribe message, just put the appropriate mailing list name rather than `mysql'. For example, to subscribe to or unsubscribe from the `myodbc' list, send a message to or . If you can't get an answer for your questions from the mailing list, one option is to pay for support from *MySQL AB*, which will put you in direct contact with *MySQL* developers. *Note Support::. The following table shows some *MySQL* mailing in other languages than English. Note that these are not operated by *MySQL AB*, so we can't guarantee the quality on these. ` A French mailing list' ` A Korean mailing list' Email `subscribe mysql your@email.address' to this list. ` A German mailing list' Email `subscribe mysql-de your@email.address' to this list. You can find information about this mailing list at `http://www.4t2.com/mysql'. ` A Portugese mailing list' Email `subscribe mysql-br your@email.address' to this list. ` A Spanish mailing list' Email `subscribe mysql your@email.address' to this list. Asking Questions or Reporting Bugs .................................. Before posting a bug report or question, please do the following: * Start by searching the *MySQL* online manual at: `http://www.mysql.com/documentation/manual.php' We try to keep the manual up to date by updating it frequently with solutions to newly found problems! * Search the *MySQL* mailing list archives: `http://www.mysql.com/documentation/' * You can also use `http://www.mysql.com/search.html' to search all the Web pages (including the manual) that are located at `http://www.mysql.com/'. If you can't find an answer in the manual or the archives, check with your local *MySQL* expert. If you still can't find an answer to your question, go ahead and read the next section about how to send mail to . How to Report Bugs or Problems .............................. Writing a good bug report takes patience, but doing it right the first time saves time for us and for you. A good bug report containing a full test case for the bug will make it very likely that we will fix it in the next release. This section will help you write your report correctly so that you don't waste your time doing things that may not help us much or at all. We encourage everyone to use the `mysqlbug' script to generate a bug report (or a report about any problem), if possible. `mysqlbug' can be found in the `scripts' directory in the source distribution, or, for a binary distribution, in the `bin' directory under your *MySQL* installation directory. If you are unable to use `mysqlbug', you should still include all the necessary information listed in this section. The `mysqlbug' script helps you generate a report by determining much of the following information automatically, but if something important is missing, please include it with your message! Please read this section carefully and make sure that all the information described here is included in your report. The normal place to report bugs and problems is . If you can make a test case that clearly demonstrates the bug, you should post it to the list. Note that on this list you should only post a full, repeatable bug report using the `mysqlbug' script. If you are running on Windows, you should include a description of the operating system and the *MySQL* version. Preferably, you should test the problem using the latest stable or development version of *MySQL* before posting! Anyone should be able to repeat the bug by just using "`mysql test < script'" on the included test case or run the shell or perl script that is included in the bug report. All bugs posted on the `bugs' list will be corrected or documented in the next *MySQL* release! If there are only small code changes involved to correct this problem, we will also post a patch that fixes the problem. Remember that it is possible to respond to a message containing too much information, but not to one containing too little. Often people omit facts because they think they know the cause of a problem and assume that some details don't matter. A good principle is: if you are in doubt about stating something, state it! It is a thousand times faster and less troublesome to write a couple of lines more in your report than to be forced to ask again and wait for the answer because you didn't include enough information the first time. The most common errors are that people don't indicate the version number of the *MySQL* distribution they are using, or don't indicate what platform they have *MySQL* installed on (including the platform version number). This is highly relevant information, and in 99 cases out of 100 the bug report is useless without it! Very often we get questions like, "Why doesn't this work for me?" then we find that the feature requested wasn't implemented in that *MySQL* version, or that a bug described in a report has been fixed already in newer *MySQL* versions. Sometimes the error is platform dependent; in such cases, it is next to impossible to fix anything without knowing the operating system and the version number of the platform. Remember also to provide information about your compiler, if it is related to the problem. Often people find bugs in compilers and think the problem is *MySQL*-related. Most compilers are under development all the time and become better version by version. To determine whether or not your problem depends on your compiler, we need to know what compiler is used. Note that every compiling problem should be regarded as a bug report and reported accordingly. It is most helpful when a good description of the problem is included in the bug report. That is, a good example of all the things you did that led to the problem and the problem itself exactly described. The best reports are those that include a full example showing how to reproduce the bug or problem. *Note Reproduceable test case::. If a program produces an error message, it is very important to include the message in your report! If we try to search for something from the archives using programs, it is better that the error message reported exactly matches the one that the program produces. (Even the case should be observed!) You should never try to remember what the error message was; instead, copy and paste the entire message into your report! If you have a problem with MyODBC, you should try to generate a MyODBC trace file. *Note MyODBC bug report::. Please remember that many of the people who will read your report will do so using an 80-column display. When generating reports or examples using the `mysql' command line tool, you should therefore use the `--vertical' option (or the `\G' statement terminator) for output that would exceed the available width for such a display (for example, with the `EXPLAIN SELECT' statement; see the example below). Please include the following information in your report: * The version number of the *MySQL* distribution you are using (for example, *MySQL* Version 3.22.22). You can find out which version you are running by executing `mysqladmin version'. `mysqladmin' can be found in the `bin' directory under your *MySQL* installation directory. * The manufacturer and model of the machine you are working on. * The operating system name and version. For most operating systems, you can get this information by executing the Unix command `uname -a'. * Sometimes the amount of memory (real and virtual) is relevant. If in doubt, include these values. * If you are using a source distribution of *MySQL*, the name and version number of the compiler used is needed. If you have a binary distribution, the distribution name is needed. * If the problem occurs during compilation, include the exact error message(s) and also a few lines of context around the offending code in the file where the error occurred. * If `mysqld' died, you should also report the query that crashed `mysqld'. You can usually find this out by running `mysqld' with logging enabled. *Note Using log files::. * If any database table is related to the problem, include the output from `mysqldump --no-data db_name tbl_name1 tbl_name2 ...'. This is very easy to do and is a powerful way to get information about any table in a database that will help us create a situation matching the one you have. * For speed-related bugs or problems with `SELECT' statements, you should always include the output of `EXPLAIN SELECT ...', and at least the number of rows that the `SELECT' statement produces. The more information you give about your situation, the more likely it is that someone can help you! For example, the following is an example of a very good bug report (it should of course be posted with the `mysqlbug' script): Example run using the `mysql' command line tool (note the use of the `\G' statement terminator for statements whose output width would otherwise exceed that of an 80-column display device): mysql> SHOW VARIABLES; mysql> SHOW COLUMNS FROM ...\G mysql> EXPLAIN SELECT ...\G mysql> FLUSH STATUS; mysql> SELECT ...; mysql> SHOW STATUS; * If a bug or problem occurs while running *mysqld*, try to provide an input script that will reproduce the anomaly. This script should include any necessary source files. The more closely the script can reproduce your situation, the better. If you can make a repeatable test case, you should post this to for a high priority treatment! If you can't provide a script, you should at least include the output from `mysqladmin variables extended-status processlist' in your mail to provide some information of how your system is performing! * If you can't produce a test case in a few rows, or if the test table is too big to be mailed to the mailing list (more than 10 rows), you should dump your tables using `mysqldump' and create a `README' file that describes your problem. Create a compressed archive of your files using `tar' and `gzip' or `zip', and use `ftp' to transfer the archive to `ftp://support.mysql.com/pub/mysql/secret/'. Then send a short description of the problem to . * If you think that *MySQL* produces a strange result from a query, include not only the result, but also your opinion of what the result should be, and an account describing the basis for your opinion. * When giving an example of the problem, it's better to use the variable names, table names, etc., that exist in your actual situation than to come up with new names. The problem could be related to the name of a variable or table! These cases are rare, perhaps, but it is better to be safe than sorry. After all, it should be easier for you to provide an example that uses your actual situation, and it is by all means better for us. In case you have data you don't want to show to others, you can use `ftp' to transfer it to `ftp://support.mysql.com/pub/mysql/secret/'. If the data are really top secret and you don't want to show them even to us, then go ahead and provide an example using other names, but please regard this as the last choice. * Include all the options given to the relevant programs, if possible. For example, indicate the options that you use when you start the `mysqld' daemon and that you use to run any *MySQL* client programs. The options to programs like `mysqld' and `mysql', and to the `configure' script, are often keys to answers and are very relevant! It is never a bad idea to include them anyway! If you use any modules, such as Perl or PHP, please include the version number(s) of those as well. * If your question is related to the privilege system, please include the output of `mysqlaccess', the output of `mysqladmin reload', and all the error messages you get when trying to connect! When you test your privileges, you should first run `mysqlaccess'. After this, execute `mysqladmin reload version' and try to connect with the program that gives you trouble. `mysqlaccess' can be found in the `bin' directory under your *MySQL* installation directory. * If you have a patch for a bug, that is good, but don't assume the patch is all we need, or that we will use it, if you don't provide some necessary information, such as test cases showing the bug that your patch fixes. We might find problems with your patch or we might not understand it at all; if so, we can't use it. If we can't verify exactly what the patch is meant for, we won't use it. Test cases will help us here. Show that the patch will handle all the situations that may occur. If we find a borderline case (even a rare one) where the patch won't work, it may be useless. * Guesses about what the bug is, why it occurs, or what it depends on, are usually wrong. Even the *MySQL* team can't guess such things without first using a debugger to determine the real cause of a bug. * Indicate in your mail message that you have checked the reference manual and mail archive so others know that you have tried to solve the problem yourself. * If you get a `parse error', please check your syntax closely! If you can't find something wrong with it, it's extremely likely that your current version of *MySQL* doesn't support the query you are using. If you are using the current version and the manual at `http://www.mysql.com/documentation/manual.php' doesn't cover the syntax you are using, *MySQL* doesn't support your query. In this case, your only options are to implement the syntax yourself or e-mail and ask for an offer to implement it! If the manual covers the syntax you are using, but you have an older version of *MySQL*, you should check the *MySQL* change history to see when the syntax was implemented. In this case, you have the option of upgrading to a newer version of *MySQL*. *Note News::. * If you have a problem such that your data appears corrupt or you get errors when you access some particular table, you should first check and then try repairing your tables with `myisamchk' or `CHECK TABLE' and `REPAIR TABLE'. *Note MySQL Database Administration::. * If you often get corrupted tables you should try to find out when and why this happens! In this case, the `mysql-data-directory/'hostname'.err' file may contain some information about what happened. *Note Error log::. Please include any relevant information from this file in your bug report! Normally `mysqld' should *NEVER* crash a table if nothing killed it in the middle of an update! If you can find the cause of `mysqld' dying, it's much easier for us to provide you with a fix for the problem! *Note What is crashing::. * If possible, download and install the most recent version of *MySQL* and check whether or not it solves your problem. All versions of *MySQL* are thoroughly tested and should work without problems! We believe in making everything as backward compatible as possible, and you should be able to switch *MySQL* versions in minutes! *Note Which version::. If you are a support customer, please cross-post the bug report to for higher priority treatment, as well as to the appropriate mailing list to see if someone else has experienced (and perhaps solved) the problem. For information on reporting bugs in *MyODBC*, see *Note ODBC Problems::. For solutions to some common problems, see *Note Problems::. When answers are sent to you individually and not to the mailing list, it is considered good etiquette to summarize the answers and send the summary to the mailing list so that others may have the benefit of responses you received that helped you solve your problem! Guidelines for Answering Question on the Mailing List ..................................................... If you consider your answer to have broad interest, you may want to post it to the mailing list instead of replying directly to the individual who asked. Try to make your answer general enough that people other than the original poster may benefit from it. When you post to the list, please make sure that your answer is not a duplication of a previous answer. Try to summarize the essential part of the question in your reply; don't feel obliged to quote the entire original message. Please don't post mail messages from your browser with HTML mode turned on! Many users don't read mail with a browser! MySQL Licensing and Support =========================== This section describes *MySQL* support and licensing arrangements: * The copyrights under which *MySQL* is distributed (*note Copyright::) * Sample situations illustrating when a license is required (*note Licensing examples::) * Support costs (*note Cost::) and support benefits (*note Support::) * Commercial licensing costs MySQL Licensing Policy ---------------------- The formal terms of the GPL license can be found at *Note GPL license::. Basically, our licensing policy and interpretation of the GPL is as follows: Note that older versions of *MySQL* are still using a more strict license (http://www.mysql.com/support/arrangements/mypl.html). See the documentation for that version for more information. If you need a commercial *MySQL* license, because the GPL license doesn't suit your application, you can buy one at `https://order.mysql.com/'. For normal internal use, *MySQL* costs nothing. You do not have to pay us if you do not want to. A license is required if: - You link a program, that is not free software, with code from the *MySQL* server or clients that has the GPL copyright. This happens for example when you use *MySQL* as an embedded server in your applications or when you add not free extensions to the *MySQL* server. In this case your application/code would also become GPL through the GPL license that acts as a virus. By licensing *MySQL* server from *MySQL AB* under a commercial license you will avoid this problem. See `http://www.gnu.org/copyleft/gpl-faq.html'. - You have a commercial application that ONLY works with *MySQL* and ships the application with the *MySQL* server. This is because we view this as linking even if it is done over the network. - You have a distribution of *MySQL* and you don't provide the source code for your copy of the *MySQL* server, as defined in the GPL license. A license is *NOT* required if: - You do not need a license to include the client code in commercial programs. The client part of *MySQL* licensed with the LGPL `GNU Library General Public License'. The `mysql' command-line client includes code from the `readline' library that is under the `GPL'. - If your use of *MySQL* does not require a license, but you like *MySQL* and want to encourage further development, you are certainly welcome to purchase a license or *MySQL* support anyway. - If you use *MySQL* in a commercial context such that you profit by its use, we ask that you further the development of *MySQL* by purchasing some level of support. We feel that if *MySQL* helps your business, it is reasonable to ask that you help *MySQL*. (Otherwise, if you ask us support questions, you are not only using for free something into which we've put a lot a work, you're asking us to provide free support, too.) For circumstances under which a *MySQL* license is required, you need a license per machine that runs the `mysqld' server. However, a multiple-CPU machine counts as a single machine, and there is no restriction on the number of *MySQL* servers that run on one machine, or on the number of clients concurrently connected to a server running on that machine! If you have any questions as to whether or not a license is required for your particular use of *MySQL*, please read this again and then contact us. *Note Contact information::. If you require a *MySQL* license, the easiest way to pay for it is to use the license form on *MySQL*'s secure server at `https://order.mysql.com/'. Other forms of payment are discussed in *Note Payment information::. Copyrights Used by MySQL ------------------------ There are several different copyrights on the *MySQL* distribution: 1. The *MySQL*-specific source needed to build the `mysqlclient' library is licensed under the `LGPL' and programs in the `client' directory is GPL. Each file has a header that shows which copyright is used for that file. 2. The client library and the (GNU `getopt') library are covered by the "GNU LIBRARY GENERAL PUBLIC LICENSE." *Note LGPL license::. 3. Some parts of the source (the `regexp' library) are covered by a Berkeley-style copyright. 4. All the source in the server and the (GNU `readline') library is covered by the "GNU GENERAL PUBLIC LICENSE." *Note GPL license::. This is also available as the file `COPYING' in the distributions. One goal is that the SQL client library should be free enough that it is possible to add *MySQL* support into commercial products without a license. For this reason, we chose the LGPL license for the client code. This means that you can use *MySQL* for free with any program that uses any of the free software licenses. *MySQL* is also free for any end user for his own or company usage. However, if you use *MySQL* for something important to you, you may want to help secure its development by purchasing licenses or a support contract. *Note Support::. Copyright Changes ................. Version 3.22 of *MySQL* is still using a more strict license. See the documentation for that version for more information. Example Licensing Situations ---------------------------- This section describes some situations illustrating whether or not you must license the *MySQL* server. Generally these examples involve providing *MySQL* as an integral part of a product. Note that a single *MySQL* license covers any number of CPUs and `mysqld' servers on a machine! There is no artificial limit on the number of clients that connect to the server in any way. Selling Products that use MySQL ............................... To determine whether or not you need a *MySQL* license when selling your application, you should ask whether the proper functioning of your application is dependent on the use of *MySQL* and whether you include the *MySQL* server with your product. There are several cases to consider: * Does your application require *MySQL* to function properly? * If your product requires *MySQL*, you need a license for any machine that runs the `mysqld' server. For example, if you've designed your application around *MySQL*, then you've really made a commercial product that requires the engine, so you need a license. * If your application does not require *MySQL*, you do not need to obtain a license. For example, if using *MySQL* just adds some new optional features to your product (such as adding logging to a database if *MySQL* is used rather than logging to a text file), it should fall within normal use, and a license would not be required. * In other words, you need a license if you sell a product designed specifically for use with *MySQL* or that requires the *MySQL* server to function at all. This is true whether or not you provide *MySQL* for your client as part of your product distribution. * It also depends on what you're doing for the client. Do you plan to provide your client with detailed instructions on installing *MySQL* with your software? Then your product may be contingent on the use of *MySQL*; if so, you need to buy a license. If you are simply tying into a database that you expect already to have been installed by the time your software is purchased, then you probably don't need a license. ISP MySQL Services .................. Internet Service Providers (ISPs) often host *MySQL* servers for their customers. With the GPL license this does not require a license. On the other hand, we do encourage people to use ISPs that have *MySQL* support, as this will give them the confidence that if they have some problem with their *MySQL* installation, their ISP will be able to solve the problem for them (in some cases with the help from the *MySQL* development team). All ISPs that want to keep themselves up-to-date should subscribe to our `announce' mailing list so that they can be aware of fatal issues that may be relevant for their *MySQL* installations. Note that if the ISP doesn't have a license for *MySQL*, it should give its customers at least read access to the source of the *MySQL* installation so that its customer can verify that it is patched correctly. Running a Web Server Using MySQL ................................ If you use *MySQL* in conjunction with a Web server on Unix, you don't have to pay for a license. This is true even if you run a commercial Web server that uses *MySQL*, because you are not selling an embedded *MySQL* version yourself. However, in this case we would like you to purchase *MySQL* support, because *MySQL* is helping your enterprise. MySQL Licensing and Support Costs --------------------------------- Our current license prices are shown below. To make a purchase, please visit `https://order.mysql.com/'. If you pay by credit card, the currency is EURO (European Union Euro) so the prices will differ slightly. *Number of licenses* *Per copy* 1-9 230 EURO 10-24 138 EURO 25-49 117 EURO 50-99 102 EURO 100-249 91 EURO 250-499 76 EURO 500-999 66 EURO For high volume (OEM) purchases, please contact . For OEM purchases, you must act as the middle-man for eventual problems or extension requests from your users. We also require that OEM customers have at least an extended e-mail support contract. Note that OEM licenses only apply for products where the user doesn't have direct access to the *MySQL* server (embedded system). In other words, the *MySQL* server should only be used with the application that was supplied you. If you have a low-margin, high-volume product, you can always talk to us about other terms (for example, a percent of the sale price). If you do, please be informative about your product, pricing, market, and any other information that may be relevant. A full-price license is not a support agreement and includes very minimal support. This means that we try to answer any relevant questions. If the answer is in the documentation, we will direct you to the appropriate section. If you have not purchased a license or support, we probably will not answer at all. If you discover what we consider a real bug, we are likely to fix it in any case. But if you pay for support we will notify you about the fix status instead of just fixing it in a later release. More comprehensive support is sold separately. Descriptions of what each level of support includes are given in *Note Support::. Costs for the various types of commercial support are shown below. Support level prices are in EURO (European Union Euro). One EURO is about 1.06 USD. *Type of support* *Cost per year* Basic e-mail support. *Note Basic EURO 200 email support::. Extended e-mail support *Note EURO 1000 Extended email support::. Login support *Note Login EURO 2000 support::. Extended login support *Note EURO 5000 Extended login support::. Telephone support *Note Telephone EURO 12000 support::. You may upgrade from any lower level of support to a higher level of support for the difference in price between the two support levels. We do also provide telephone support (mostly emergency support but also 24/7 support). This support option doesn't however have a fixed price but is negotiated for case to case. If you are interested in this option you can email and tell us about your needs. Note that as our sales staff is very busy, it may take some time until your request is handled. Our support staff does however always answer promptly to support questions! Payment information ................... Currently we can take SWIFT payments, checks, or credit cards. Payment should be made to: Postgirot Bank AB 105 06 STOCKHOLM, SWEDEN MySQL AB BOX 6434 11382 STOCKHOLM, SWEDEN SWIFT address: PGSI SESS Account number: 96 77 06 - 3 Specify: license and/or support and your name and e-mail address. In Europe and Japan you can use EuroGiro (that should be less expensive) to the same account. If you want to pay by check, make it payable to "MySQL Finland AB" and mail it to the address below: MySQL AB BOX 6434, Torsgatan 21 11382 STOCKHOLM, SWEDEN If you want to pay by credit card over the Internet, you can use MySQL AB's secure license form (https://order.mysql.com/). You can also print a copy of the license form, fill it in, and send it by fax to: +46-8-729 69 05 If you want us to bill you, you can use the license form and write "bill us" in the comment field. You can also mail a message to (*not* `mysql@lists.mysql.com'!) with your company information and ask us to bill you. Contact Information ................... For commercial licensing, please contact the *MySQL* licensing team. The much preferred method is by e-mail to . Fax is also possible but handling of these may take much longer (Fax +46-8-729 69 05). If you represent a business that is interested in partnering with *MySQL*, please send e-mail to . For timely, precise answers to technical questions about *MySQL* you should order (https://order.mysql.com/) one of our support contracts (http://www.mysql.com/support/arrangements/types.html). *MySQL* support is provided by the *MySQL* developers so the standard is extremely high. If you are interested in placing a banner advertisement on our Web site, please send e-mail to . If you are interested in any of the jobs listed in our jobs (http://www.mysql.com/development/jobs/) section, please send e-mail to . For general discussion amongst our many users, please direct your attention to the appropriate mailing list (http://www.mysql.com/documentation/lists.html). For general information inquires, please send e-mail to . For questions or comments about the workings or content of the Web site, please send e-mail to . Types of Commercial Support --------------------------- The following is true of all support options: * The support is per year. * We will fix, or provide a reasonable workaround for any repeatable bug. * We will give a reasonable effort to find and fix any other MySQL related bug. * The higher level of support contract the more effort we will put into finding a solution to your problems. * The following is true for all support contracts except Basic email support: For non-bug related things, like helping you optimize your queries or your system, extending MySQL with new functionality, etc., we charge 200 EURO/hour, which is deducted from your support contract. In other words, if you have login support (2000 EURO), you can expect us to work up to 10 hours to help you with things like this. Basic E-mail Support .................... Basic e-mail support is a very inexpensive support option and should be thought of more as a way to support our development of *MySQL* than as a real support option. We at *MySQL* do give a lot of free support in all the different *MySQL* lists, and the money we get from basic e-mail support is largely used to make this possible. At this support level, the *MySQL* mailing lists are the preferred means of communication. Questions normally should be mailed to the primary mailing list () or one of the other regular lists (for example, for Windows-related *MySQL* questions), as someone else already may have experienced and solved the problem you have. *Note Asking questions::. However, by purchasing basic e-mail support, you also have access to the support address , which is not available as part of the minimal support that you get by purchasing a *MySQL* license. This means that for especially critical questions, you can cross-post your message to . (If the message contains sensitive data, you should post only to .) *REMEMBER!* to ALWAYS include your registration number and expiration date when you send a message to . Note that if you have encountered a critical, repeatable bug, and follow the rules outlined in the manual section of how to report bugs and send it to , we promise to try to fix this as soon as possible, regardless of your support level! *Note Bug reports::. Basic e-mail support includes the following types of service: * If your question is already answered in the manual, we will inform you of the correct section in which you can find the answer. If the answer is not in the manual, we will point you in the right direction to solve your problem. * We guarantee a timely answer for your e-mail messages. We can't guarantee that we can solve any problem, but at least you will receive an answer if we can contact you by e-mail. * We will help with unexpected problems when you install *MySQL* from a binary distribution on supported platforms. This level of support does not cover installing *MySQL* from a source distribution. Supported platforms are those for which *MySQL* is known to work. *Note Which OS::. * We will help you with bugs and missing features. Any bugs that are found are fixed for the next *MySQL* release. If the bug is critical for you, we will mail you a patch for it as soon the bug is fixed. Critical bugs always have the highest priority for us, and we ensure that they are fixed as soon as possible. * Your suggestions for the further development of *MySQL* will be taken into consideration. By taking email support you have already helped the further development of *MySQL*. If you want to have more input, upgrade to a higher level of support. * If you want us to help optimize your system, you must upgrade to a higher level of support. Extended E-mail Support ....................... Extended e-mail support includes everything in basic e-mail support with these additions: * Your e-mail will be dealt with before mail from basic e-mail support users and non-registered users. * Your suggestions for the further development of *MySQL* will receive strong consideration. Simple extensions that suit the basic goals of *MySQL* are implemented in a matter of days. By taking extended e-mail support you have already helped the further development of *MySQL*. * Typical situations that are covered by extended e-mail support are: - We will answer and (within reason) solve questions that relate to possible bugs in *MySQL*. As soon as the bug is found and corrected, we will mail a patch for it. - We will help with unexpected problems when you install *MySQL* from a source or binary distribution on supported platforms. - We will answer questions about missing features and offer hints how to work around them. - We will provide hints on optimizing `mysqld' for your situation. * You are allowed to influence the priority of items on the *MySQL* TODO List. *Note TODO::. This will ensure that the features you really need will be implemented sooner than they might be otherwise. Login Support ............. Login support includes everything in extended e-mail support with these additions: * Your e-mail will be dealt with even before e-mail from extended e-mail support users. * Your suggestions for the further development of *MySQL* will be taken into very high consideration. Realistic extensions that can be implemented in a couple of hours and that suit the basic goals of *MySQL* will be implemented as soon as possible. * If you have a very specific problem, we can try to log in on your system to solve the problem "in place." * Like any database vendor, we can't guarantee that we can rescue any data from crashed tables, but if the worst happens, we will help you rescue as much as possible. *MySQL* has proven itself very reliable, but anything is possible due to circumstances beyond our control (for example, if your system crashes or someone kills the server by executing a `kill -9' command). * We will provide hints on optimizing your system and your queries. * You are allowed to call a *MySQL* developer (in moderation) and discuss your *MySQL*-related problems. This option is however only to be used as a last result during an emergency after we have failed to grasp the total problem with email. To make efficient use of our time we need to first get all facts about the problem, before talking on phone, to be able to work as efficiently as possible on solving the problem. Extended Login Support ...................... Extended login support includes everything in login support with these additions: * Your e-mail has the highest possible priority. * We will actively examine your system and help you optimize it and your queries. We may also optimize and/or extend *MySQL* to better suit your needs. * You may also request special extensions just for you. For example: mysql> select MY_FUNC(col1,col2) from table; * We will provide a binary distribution of all important *MySQL* releases for your system, as long as we can get an account on a similar system. In the worst case, we may require access to your system to be able to create a binary distribution. * If you can provide accommodations and pay for traveler fares, you can even get a *MySQL* developer to visit you and offer you help with your troubles. Extended login support entitles you to one personal encounter per year, but we are always very flexible towards our customers! If the visit takes 16 hours or more, the first 8 hours is without charge. For the hours above 8 hours, you will be charged with a rate that is at least 20 % less than our standard rates. Telephone Support ................. Telephone support includes everything in extended login support with these additions: * We will provide you with a dynamic web page showing the current list of `MySQL' developers that you can phone when you have a critical problem. * For non critical problem, you can request a *MySQL* developer to phone back within 48 hours to discuss `MySQL' related issues. Support for other table handlers ................................ To get support for `BDB' tables, `InnoDB' tables you have to pay an additional 30% on the standard support price for each of the table handlers you would like to have support for. We at `MySQL AB' will help you create a proper bug report for the table handler and submit it to the developers for the specific table handler. We will also do our best to ensure that you will get a timely answer or solution from the developers of the table handler. Even if we are quite confident that we can solve most problems within a timely manner, we can't guarantee a quick solution for any problems you can get with the different table handlers. We will however do our best to help you get the problem solved. How Standards-compatible Is MySQL? ================================== This section describes how *MySQL* relates to the ANSI SQL standards. *MySQL* has many extensions to the ANSI SQL standards, and here you will find out what they are, and how to use them. You will also find information about functionality missing from *MySQL*, and how to work around some differences. MySQL Extensions to ANSI SQL92 ------------------------------ *MySQL* includes some extensions that you probably will not find in other SQL databases. Be warned that if you use them, your code will not be portable to other SQL servers. In some cases, you can write code that includes *MySQL* extensions, but is still portable, by using comments of the form `/*! ... */'. In this case, *MySQL* will parse and execute the code within the comment as it would any other *MySQL* statement, but other SQL servers will ignore the extensions. For example: SELECT /*! STRAIGHT_JOIN */ col_name FROM table1,table2 WHERE ... If you add a version number after the `'!'', the syntax will only be executed if the *MySQL* version is equal to or newer than the used version number: CREATE /*!32302 TEMPORARY */ TABLE (a int); The above means that if you have Version 3.23.02 or newer, then *MySQL* will use the `TEMPORARY' keyword. *MySQL* extensions are listed below: * The field types `MEDIUMINT', `SET', `ENUM', and the different `BLOB' and `TEXT' types. * The field attributes `AUTO_INCREMENT', `BINARY', `NULL', `UNSIGNED', and `ZEROFILL'. * All string comparisons are case insensitive by default, with sort ordering determined by the current character set (ISO-8859-1 Latin1 by default). If you don't like this, you should declare your columns with the `BINARY' attribute or use the `BINARY' cast, which causes comparisons to be done according to the ASCII order used on the *MySQL* server host. * *MySQL* maps each database to a directory under the *MySQL* data directory, and tables within a database to filenames in the database directory. This has a few implications: - Database names and table names are case sensitive in *MySQL* on operating systems that have case-sensitive filenames (like most Unix systems). *Note Name case sensitivity::. - Database, table, index, column, or alias names may begin with a digit (but may not consist solely of digits). - You can use standard system commands to backup, rename, move, delete, and copy tables. For example, to rename a table, rename the `.MYD', `.MYI', and `.frm' files to which the table corresponds. * In SQL statements, you can access tables from different databases with the `db_name.tbl_name' syntax. Some SQL servers provide the same functionality but call this `User space'. *MySQL* doesn't support tablespaces as in: `create table ralph.my_table...IN my_tablespace'. * `LIKE' is allowed on numeric columns. * Use of `INTO OUTFILE' and `STRAIGHT_JOIN' in a `SELECT' statement. *Note `SELECT': SELECT. * The `SQL_SMALL_RESULT' option in a `SELECT' statement. * `EXPLAIN SELECT' to get a description on how tables are joined. * Use of index names, indexes on a prefix of a field, and use of `INDEX' or `KEY' in a `CREATE TABLE' statement. *Note `CREATE TABLE': CREATE TABLE. * Use of `TEMPORARY' or `IF NOT EXISTS' with `CREATE TABLE'. * Use of `COUNT(DISTINCT list)' where 'list' is more than one element. * Use of `CHANGE col_name', `DROP col_name', or `DROP INDEX', `IGNORE' or `RENAME' in an `ALTER TABLE' statement. *Note `ALTER TABLE': ALTER TABLE. * Use of `RENAME TABLE'. *Note `RENAME TABLE': RENAME TABLE. * Use of multiple `ADD', `ALTER', `DROP', or `CHANGE' clauses in an `ALTER TABLE' statement. * Use of `DROP TABLE' with the keywords `IF EXISTS'. * You can drop multiple tables with a single `DROP TABLE' statement. * The `LIMIT' clause of the `DELETE' statement. * The `DELAYED' clause of the `INSERT' and `REPLACE' statements. * The `LOW_PRIORITY' clause of the `INSERT', `REPLACE', `DELETE', and `UPDATE' statements. * Use of `LOAD DATA INFILE'. In many cases, this syntax is compatible with Oracle's `LOAD DATA INFILE'. *Note `LOAD DATA': LOAD DATA. * The `ANALYZE TABLE', `CHECK TABLE', `OPTIMIZE TABLE', and `REPAIR TABLE' statements. * The `SHOW' statement. *Note `SHOW': SHOW. * Strings may be enclosed by either `"' or `'', not just by `''. * Use of the escape `\' character. * The `SET OPTION' statement. *Note `SET OPTION': SET OPTION. * You don't need to name all selected columns in the `GROUP BY' part. This gives better performance for some very specific, but quite normal queries. *Note Group by functions::. * One can specify `ASC' and `DESC' with `GROUP BY'. * To make it easier for users who come from other SQL environments, *MySQL* supports aliases for many functions. For example, all string functions support both ANSI SQL syntax and ODBC syntax. * *MySQL* understands the `||' and `&&' operators to mean logical OR and AND, as in the C programming language. In *MySQL*, `||' and `OR' are synonyms, as are `&&' and `AND'. Because of this nice syntax, *MySQL* doesn't support the ANSI SQL `||' operator for string concatenation; use `CONCAT()' instead. Because `CONCAT()' takes any number of arguments, it's easy to convert use of the `||' operator to *MySQL*. * `CREATE DATABASE' or `DROP DATABASE'. *Note `CREATE DATABASE': CREATE DATABASE. * The `%' operator is a synonym for `MOD()'. That is, `N % M' is equivalent to `MOD(N,M)'. `%' is supported for C programmers and for compatibility with PostgreSQL. * The `=', `<>', `<=' ,`<', `>=',`>', `<<', `>>', `<=>', `AND', `OR', or `LIKE' operators may be used in column comparisons to the left of the `FROM' in `SELECT' statements. For example: mysql> SELECT col1=1 AND col2=2 FROM tbl_name; * The `LAST_INSERT_ID()' function. *Note `mysql_insert_id()': mysql_insert_id. * The `REGEXP' and `NOT REGEXP' extended regular expression operators. * `CONCAT()' or `CHAR()' with one argument or more than two arguments. (In *MySQL*, these functions can take any number of arguments.) * The `BIT_COUNT()', `CASE', `ELT()', `FROM_DAYS()', `FORMAT()', `IF()', `PASSWORD()', `ENCRYPT()', `md5()', `ENCODE()', `DECODE()', `PERIOD_ADD()', `PERIOD_DIFF()', `TO_DAYS()', or `WEEKDAY()' functions. * Use of `TRIM()' to trim substrings. ANSI SQL only supports removal of single characters. * The `GROUP BY' functions `STD()', `BIT_OR()', and `BIT_AND()'. * Use of `REPLACE' instead of `DELETE' + `INSERT'. *Note `REPLACE': REPLACE. * The `FLUSH flush_option' statement. * The possibility to set variables in a statement with `:=': SELECT @a:=SUM(total),@b=COUNT(*),@a/@b AS avg FROM test_table; SELECT @t1:=(@t2:=1)+@t3:=4,@t1,@t2,@t3; MySQL Differences Compared to ANSI SQL92 ---------------------------------------- We try to make *MySQL* follow the ANSI SQL standard and the ODBC SQL standard, but in some cases *MySQL* does some things differently: * `--' is only a comment if followed by a white space. *Note Missing comments::. * For `VARCHAR' columns, trailing spaces are removed when the value is stored. *Note Bugs::. * In some cases, `CHAR' columns are silently changed to `VARCHAR' columns. *Note Silent column changes::. * Privileges for a table are not automatically revoked when you delete a table. You must explicitly issue a `REVOKE' to revoke privileges for a table. *Note `GRANT': GRANT. * `NULL AND FALSE' will evaluate to `NULL' and not to `FALSE'. This is because we don't think it's good to have to evaluate a lot of extra conditions in this case. Running MySQL in ANSI Mode -------------------------- If you start `mysqld' with the `--ansi' option, the following behavior of *MySQL* changes: * `||' is string concatenation instead of `OR'. * You can have any number of spaces between a function name and the `('. This forces all function names to be treated as reserved words. * `"' will be an identifier quote character (like the *MySQL* ``' quote character) and not a string quote character. * `REAL' will be a synonym for `FLOAT' instead of a synonym of `DOUBLE'. * The default transaction isolation level is `SERIALIZABLE'. *Note SET TRANSACTION::. This is the same as using `--sql-mode=REAL_AS_FLOAT,PIPES_AS_CONCAT,ANSI_QUOTES,IGNORE_SPACE,SERIALIZE,ONLY_FULL_GROUP_BY'. Functionality Missing from MySQL -------------------------------- The following functionality is missing in the current version of *MySQL*. For a prioritized list indicating when new extensions may be added to *MySQL*, you should consult the online *MySQL* TODO list (http://www.mysql.com/documentation/manual.php?section=TODO). That is the latest version of the TODO list in this manual. *Note TODO::. Sub-selects ........... The following will not yet work in *MySQL*: SELECT * FROM table1 WHERE id IN (SELECT id FROM table2); SELECT * FROM table1 WHERE id NOT IN (SELECT id FROM table2); SELECT * FROM table1 WHERE NOT EXISTS (SELECT id FROM table2 where table1.id=table2.id); However, in many cases you can rewrite the query without a sub-select: SELECT table1.* FROM table1,table2 WHERE table1.id=table2.id; SELECT table1.* FROM table1 LEFT JOIN table2 ON table1.id=table2.id where table2.id IS NULL For more complicated subqueries you can often create temporary tables to hold the subquery. In some cases, however this option will not work. The most frequently encountered of these cases arises with `DELETE' statements, for which standard SQL does not support joins (except in sub-selects). For this situation there are two options available until subqueries are supported by *MySQL*. The first option is to use a procedural programming language (such as Perl or PHP) to submit a `SELECT' query to obtain the primary keys for the records to be deleted, and then use these values to construct the `DELETE' statement (`DELETE FROM ... WHERE ... IN (key1, key2, ...)'). The second option is to use interactive SQL to contruct a set of `DELETE' statements automatically, using the *MySQL* extension `CONCAT()' (in lieu of the standard `||' operator). For example: SELECT CONCAT('DELETE FROM tab1 WHERE pkid = ', tab1.pkid, ';') FROM tab1, tab2 WHERE tab1.col1 = tab2.col2; You can place this query in a script file and redirect input from it to the `mysql' command-line interpreter, piping its output back to a second instance of the interpreter: prompt> mysql --skip-column-names mydb < myscript.sql | mysql mydb *MySQL* only supports `INSERT ... SELECT ...' and `REPLACE ... SELECT ...' Independent sub-selects will probably be available in Version 4.0. You can now use the function `IN()' in other contexts, however. `SELECT INTO TABLE' ................... *MySQL* doesn't yet support the Oracle SQL extension: `SELECT ... INTO TABLE ...'. *MySQL* supports instead the ANSI SQL syntax `INSERT INTO ... SELECT ...', which is basically the same thing. *Note INSERT SELECT::. INSERT INTO tblTemp2 (fldID) SELECT tblTemp1.fldOrder_ID FROM tblTemp1 WHERE tblTemp1.fldOrder_ID > 100; Alternatively, you can use `SELECT INTO OUTFILE...' or `CREATE TABLE ... SELECT' to solve your problem. Transactions ............ As *MySQL* does nowadays support transactions, the following discussion is only valid if you are only using the non-transaction-safe table types. *Note COMMIT::. The question is often asked, by the curious and the critical, "Why is *MySQL* not a transactional database?" or "Why does *MySQL* not support transactions?" *MySQL* has made a conscious decision to support another paradigm for data integrity, "atomic operations." It is our thinking and experience that atomic operations offer equal or even better integrity with much better performance. We, nonetheless, appreciate and understand the transactional database paradigm and plan, within the next few releases, to introduce transaction-safe tables on a per table basis. We will be giving our users the possibility to decide if they need the speed of atomic operations or if they need to use transactional features in their applications. How does one use the features of *MySQL* to maintain rigorous integrity and how do these features compare with the transactional paradigm? First, in the transactional paradigm, if your applications are written in a way that is dependent on the calling of "rollback" instead of "commit" in critical situations, then transactions are more convenient. Moreover, transactions ensure that unfinished updates or corrupting activities are not committed to the database; the server is given the opportunity to do an automatic rollback and your database is saved. *MySQL*, in almost all cases, allows you to solve for potential problems by including simple checks before updates and by running simple scripts that check the databases for inconsistencies and automatically repair or warn if such occurs. Note that just by using the *MySQL* log or even adding one extra log, one can normally fix tables perfectly with no data integrity loss. Moreover, fatal transactional updates can be rewritten to be atomic. In fact,we will go so far as to say that all integrity problems that transactions solve can be done with `LOCK TABLES' or atomic updates, ensuring that you never will get an automatic abort from the database, which is a common problem with transactional databases. Not even transactions can prevent all loss if the server goes down. In such cases even a transactional system can lose data. The difference between different systems lies in just how small the time-lap is where they could lose data. No system is 100% secure, only "secure enough." Even Oracle, reputed to be the safest of transactional databases, is reported to sometimes lose data in such situations. To be safe with *MySQL*, you only need to have backups and have the update logging turned on. With this you can recover from any situation that you could with any transactional database. It is, of course, always good to have backups, independent of which database you use. The transactional paradigm has its benefits and its drawbacks. Many users and application developers depend on the ease with which they can code around problems where an abort appears to be, or is necessary, and they may have to do a little more work with *MySQL* to either think differently or write more. If you are new to the atomic operations paradigm, or more familiar or more comfortable with transactions, do not jump to the conclusion that *MySQL* has not addressed these issues. Reliability and integrity are foremost in our minds. Recent estimates indicate that there are more than 1,000,000 `mysqld' servers currently running, many of which are in production environments. We hear very, very seldom from our users that they have lost any data, and in almost all of those cases user error is involved. This is, in our opinion, the best proof of *MySQL*'s stability and reliability. Lastly, in situations where integrity is of highest importance, *MySQL*'s current features allow for transaction-level or better reliability and integrity. If you lock tables with `LOCK TABLES', all updates will stall until any integrity checks are made. If you only obtain a read lock (as opposed to a write lock), then reads and inserts are still allowed to happen. The new inserted records will not be seen by any of the clients that have a `READ' lock until they release their read locks. With `INSERT DELAYED' you can queue inserts into a local queue, until the locks are released, without having the client wait for the insert to complete. *Note INSERT DELAYED::. "Atomic," in the sense that we mean it, is nothing magical. It only means that you can be sure that while each specific update is running, no other user can interfere with it, and there will never be an automatic rollback (which can happen on transaction based systems if you are not very careful). *MySQL* also guarantees that there will not be any dirty reads. You can find some example of how to write atomic updates in the commit-rollback section. *Note Commit-rollback::. We have thought quite a bit about integrity and performance, and we believe that our atomic operations paradigm allows for both high reliability and extremely high performance, on the order of three to five times the speed of the fastest and most optimally tuned of transactional databases. We didn't leave out transactions because they are hard to do. The main reason we went with atomic operations as opposed to transactions is that by doing this we could apply many speed optimizations that would not otherwise have been possible. Many of our users who have speed foremost in their minds are not at all concerned about transactions. For them transactions are not an issue. For those of our users who are concerned with or have wondered about transactions vis-a-vis *MySQL*, there is a "*MySQL* way" as we have outlined above. For those where safety is more important than speed, we recommend them to use the `BDB', or `InnoDB' tables for all their critical data. *Note Table types::. One final note: We are currently working on a safe replication schema that we believe to be better than any commercial replication system we know of. This system will work most reliably under the atomic operations, non-transactional, paradigm. Stay tuned. Stored Procedures and Triggers .............................. A stored procedure is a set of SQL commands that can be compiled and stored in the server. Once this has been done, clients don't need to keep reissuing the entire query but can refer to the stored procedure. This provides better performance because the query has to be parsed only once, and less information needs to be sent between the server and the client. You can also raise the conceptual level by having libraries of functions in the server. A trigger is a stored procedure that is invoked when a particular event occurs. For example, you can install a stored procedure that is triggered each time a record is deleted from a transaction table and that automatically deletes the corresponding customer from a customer table when all his transactions are deleted. The planned update language will be able to handle stored procedures, but without triggers. Triggers usually slow down everything, even queries for which they are not needed. To see when *MySQL* might get stored procedures, see *Note TODO::. Foreign Keys ............ Note that foreign keys in SQL are not used to join tables, but are used mostly for checking referential integrity (foreign key constraints). If you want to get results from multiple tables from a `SELECT' statement, you do this by joining tables: SELECT * from table1,table2 where table1.id = table2.id; *Note `JOIN': JOIN. *Note example-Foreign keys::. The `FOREIGN KEY' syntax in *MySQL* exists only for compatibility with other SQL vendors' `CREATE TABLE' commands; it doesn't do anything. The `FOREIGN KEY' syntax without `ON DELETE ...' is mostly used for documentation purposes. Some ODBC applications may use this to produce automatic `WHERE' clauses, but this is usually easy to override. `FOREIGN KEY' is sometimes used as a constraint check, but this check is unnecessary in practice if rows are inserted into the tables in the right order. *MySQL* only supports these clauses because some applications require them to exist (regardless of whether or not they work). In *MySQL*, you can work around the problem of `ON DELETE ...' not being implemented by adding the appropriate `DELETE' statement to an application when you delete records from a table that has a foreign key. In practice this is as quick (in some cases quicker) and much more portable than using foreign keys. In the near future we will extend the `FOREIGN KEY' implementation so that at least the information will be saved in the table specification file and may be retrieved by `mysqldump' and ODBC. At a later stage we will implement the foreign key constraints for application that can't easily be coded to avoid them. Reasons NOT to Use Foreign Keys constraints ........................................... There are so many problems with foreign key constraints that we don't know where to start: * Foreign key constraints make life very complicated, because the foreign key definitions must be stored in a database and implementing them would destroy the whole "nice approach" of using files that can be moved, copied, and removed. * The speed impact is terrible for `INSERT' and `UPDATE' statements, and in this case almost all `FOREIGN KEY' constraint checks are useless because you usually insert records in the right tables in the right order, anyway. * There is also a need to hold locks on many more tables when updating one table, because the side effects can cascade through the entire database. It's MUCH faster to delete records from one table first and subsequently delete them from the other tables. * You can no longer restore a table by doing a full delete from the table and then restoring all records (from a new source or from a backup). * If you use foreign key constraints you can't dump and restore tables unless you do so in a very specific order. * It's very easy to do "allowed" circular definitions that make the tables impossible to re-create each table with a single create statement, even if the definition works and is usable. * It's very easy to overlook `FOREIGN KEY ... ON DELETE' rules when one codes an application. It's not unusual that one loses a lot of important information just because a wrong or misused `ON DELETE' rule. The only nice aspect of `FOREIGN KEY' is that it gives ODBC and some other client programs the ability to see how a table is connected and to use this to show connection diagrams and to help in building applications. *MySQL* will soon store `FOREIGN KEY' definitions so that a client can ask for and receive an answer about how the original connection was made. The current `.frm' file format does not have any place for it. At a later stage we will implement the foreign key constraints for application that can't easily be coded to avoid them. Views ..... *MySQL* doesn't yet support views, but we plan to implement these to about 4.1. Views are mostly useful for letting users access a set of relations as one table (in read-only mode). Many SQL databases don't allow one to update any rows in a view, but you have to do the updates in the separate tables. As *MySQL* is mostly used in applications and on web system where the application writer has full control on the database usage, most of our users haven't regarded views to be very important. (At least no one has been interested enough in this to be prepared to finance the implementation of views). One doesn't need views in *MySQL* to restrict access to columns as *MySQL* has a very sophisticated privilege system. *Note Privilege system::. `--' as the Start of a Comment .............................. Some other SQL databases use `--' to start comments. *MySQL* has `#' as the start comment character, even if the `mysql' command-line tool removes all lines that start with `--'. You can also use the C comment style `/* this is a comment */' with *MySQL*. *Note Comments::. *MySQL* Version 3.23.3 and above supports the `--' comment style only if the comment is followed by a space. This is because this degenerate comment style has caused many problems with automatically generated SQL queries that have used something like the following code, where we automatically insert the value of the payment for `!payment!': UPDATE tbl_name SET credit=credit-!payment! What do you think will happen when the value of `payment' is negative? Because `1--1' is legal in SQL, we think it is terrible that `--' means start comment. In *MySQL* Version 3.23 you can, however, use: `1-- This is a comment' The following discussion only concerns you if you are running a *MySQL* version earlier than Version 3.23: If you have a SQL program in a text file that contains `--' comments you should use: shell> replace " --" " #" < text-file-with-funny-comments.sql \ | mysql database instead of the usual: shell> mysql database < text-file-with-funny-comments.sql You can also edit the command file "in place" to change the `--' comments to `#' comments: shell> replace " --" " #" -- text-file-with-funny-comments.sql Change them back with this command: shell> replace " #" " --" -- text-file-with-funny-comments.sql What Standards Does MySQL Follow? --------------------------------- Entry level SQL92. ODBC levels 0-2. How to Cope Without `COMMIT'/`ROLLBACK' --------------------------------------- The following mostly applies only for `ISAM', `MyISAM', and `HEAP' tables. If you only use transaction-safe tables (`BDB', or `InnoDB' tables) in an an update, you can do `COMMIT' and `ROLLBACK' also with *MySQL*. *Note COMMIT::. The problem with handling `COMMIT'-`ROLLBACK' efficiently with the above table types would require a completely different table layout than *MySQL* uses today. The table type would also need extra threads that do automatic cleanups on the tables, and the disk usage would be much higher. This would make these table types about 2-4 times slower than they are today. For the moment, we prefer implementing the SQL server language (something like stored procedures). With this you would very seldom really need `COMMIT'-`ROLLBACK.' This would also give much better performance. Loops that need transactions normally can be coded with the help of `LOCK TABLES', and you don't need cursors when you can update records on the fly. We at TcX had a greater need for a real fast database than a 100% general database. Whenever we find a way to implement these features without any speed loss, we will probably do it. For the moment, there are many more important things to do. Check the TODO for how we prioritize things at the moment. (Customers with higher levels of support can alter this, so things may be reprioritized.) The current problem is actually `ROLLBACK'. Without `ROLLBACK', you can do any kind of `COMMIT' action with `LOCK TABLES'. To support `ROLLBACK' with the above table types, *MySQL* would have to be changed to store all old records that were updated and revert everything back to the starting point if `ROLLBACK' was issued. For simple cases, this isn't that hard to do (the current `isamlog' could be used for this purpose), but it would be much more difficult to implement `ROLLBACK' for `ALTER/DROP/CREATE TABLE'. To avoid using `ROLLBACK', you can use the following strategy: 1. Use `LOCK TABLES ...' to lock all the tables you want to access. 2. Test conditions. 3. Update if everything is okay. 4. Use `UNLOCK TABLES' to release your locks. This is usually a much faster method than using transactions with possible `ROLLBACK's, although not always. The only situation this solution doesn't handle is when someone kills the threads in the middle of an update. In this case, all locks will be released but some of the updates may not have been executed. You can also use functions to update records in a single operation. You can get a very efficient application by using the following techniques: * Modify fields relative to their current value. * Update only those fields that actually have changed. For example, when we are doing updates to some customer information, we update only the customer data that has changed and test only that none of the changed data, or data that depend on the changed data, has changed compared to the original row. The test for changed data is done with the `WHERE' clause in the `UPDATE' statement. If the record wasn't updated, we give the client a message: "Some of the data you have changed have been changed by another user". Then we show the old row versus the new row in a window, so the user can decide which version of the customer record he should use. This gives us something that is similar to column locking but is actually even better, because we only update some of the columns, using values that are relative to their current values. This means that typical `UPDATE' statements look something like these: UPDATE tablename SET pay_back=pay_back+'relative change'; UPDATE customer SET customer_date='current_date', address='new address', phone='new phone', money_he_owes_us=money_he_owes_us+'new_money' WHERE customer_id=id AND address='old address' AND phone='old phone'; As you can see, this is very efficient and works even if another client has changed the values in the `pay_back' or `money_he_owes_us' columns. In many cases, users have wanted `ROLLBACK' and/or `LOCK TABLES' for the purpose of managing unique identifiers for some tables. This can be handled much more efficiently by using an `AUTO_INCREMENT' column and either the SQL function `LAST_INSERT_ID()' or the C API function `mysql_insert_id()'. *Note `mysql_insert_id()': mysql_insert_id. At *MySQL AB*, we have never had any need for row-level locking because we have always been able to code around it. Some cases really need row locking, but they are very few. If you want row-level locking, you can use a flag column in the table and do something like this: UPDATE tbl_name SET row_flag=1 WHERE id=ID; *MySQL* returns 1 for the number of affected rows if the row was found and `row_flag' wasn't already 1 in the original row. You can think of it as *MySQL* changed the above query to: UPDATE tbl_name SET row_flag=1 WHERE id=ID and row_flag <> 1; Known errors and design deficiencies in MySQL --------------------------------------------- The following problems are known and have a very high priority to get fixed: * `ANALYZE TABLE' on a BDB table may in some case make the table unusable until one has restarted `mysqld'. When this happens you will see errors like the following in the *MySQL* error file: 001207 22:07:56 bdb: log_flush: LSN past current end-of-log * Don't execute `ALTER TABLE' on a `BDB' table on which you are running not completed multi-statement transactions. (The transaction will probably be ignored). * `ANALYZE TABLE', `OPTIMIZE TABLE' and `REPAIR TABLE' may cause problems on tables for which you are using `INSERT DELAYED'. * Doing a `LOCK TABLE ..' and `FLUSH TABLES ..' doesn't guarantee that there isn't a half-finished transaction in progress on the table. * BDB tables are a bit slow to open. If you have many BDB tables in a database, it will take a long time to use the `mysql' client on the database if you are not using the `-A' option or if you are using `rehash'. This is especially notable when you have a big table cache. * Th current replication protocol cannot deal with `LOAD DATA INFILE' and line terminator characters of more than 1 character. The following problems are known and will be fixed in due time: * For the moment `MATCH' only works with `SELECT' statements. * When using `SET CHARACTER SET', one can't use translated characters in database, table and column names. * `DELETE FROM merge_table' used without a `WHERE' will only clear the mapping for the table, not delete everything in the mapped tables * You cannot build in another directory when using MIT-pthreads. Because this requires changes to MIT-pthreads, we are not likely to fix this. * `BLOB' values can't "reliably" be used in `GROUP BY' or `ORDER BY' or `DISTINCT'. Only the first `max_sort_length' bytes (default 1024) are used when comparing `BLOB'bs in these cases. This can be changed with the `-O max_sort_length' option to `mysqld'. A workaround for most cases is to use a substring: `SELECT DISTINCT LEFT(blob,2048) FROM tbl_name'. * Calculation is done with `BIGINT' or `DOUBLE' (both are normally 64 bits long). It depends on the function which precision one gets. The general rule is that bit functions are done with `BIGINT' precision, `IF', and `ELT()' with `BIGINT' or `DOUBLE' precision and the rest with `DOUBLE' precision. One should try to avoid using bigger unsigned long long values than 63 bits (9223372036854775807) for anything else than bit fields! * All string columns, except `BLOB' and `TEXT' columns, automatically have all trailing spaces removed when retrieved. For `CHAR' types this is okay, and may be regarded as a feature according to ANSI SQL92. The bug is that in *MySQL*, `VARCHAR' columns are treated the same way. * You can only have up to 255 `ENUM' and `SET' columns in one table. * `safe_mysqld' re-directs all messages from `mysqld' to the `mysqld' log. One problem with this is that if you execute `mysqladmin refresh' to close and reopen the log, `stdout' and `stderr' are still redirected to the old log. If you use `--log' extensively, you should edit `safe_mysqld' to log to `'hostname'.err' instead of `'hostname'.log' so you can easily reclaim the space for the old log by deleting the old one and executing `mysqladmin refresh'. * In the `UPDATE' statement, columns are updated from left to right. If you refer to an updated column, you will get the updated value instead of the original value. For example: mysql> UPDATE tbl_name SET KEY=KEY+1,KEY=KEY+1; will update `KEY' with `2' instead of with `1'. * You can't use temporary tables more than once in the same query. For example, the following doesn't work. select * from temporary_table, temporary_table as t2; * `RENAME' doesn't work with `TEMPORARY' tables. * The optimizer may handle `DISTINCT' differently if you are using 'hidden' columns in a join or not. In a join, hidden columns are counted as part of the result (even if they are not shown) while in normal queries hidden columns doesn't participate in the `DISTINCT' comparison. We will probably change this in the future to never compare the hidden columns when executing `DISTINCT' An example of this is: SELECT DISTINCT mp3id FROM band_downloads WHERE userid = 9 ORDER BY id DESC; and SELECT DISTINCT band_downloads.mp3id, FROM band_downloads,band_mp3 WHERE band_downloads.userid = 9 AND band_mp3.id = band_downloads.mp3id ORDER BY band_downloads.id DESC; In the second case you may in *MySQL* 3.23.x get two identical rows in the result set (because the hidden 'id' column may differ). Note that the this only happens for queries where you don't have the ORDER BY columns in the result, something that is you are not allowed to do in ANSI SQL. * Because *MySQL* allows you to work with table types that doesn't support transactions (and thus can't `rollback' data) some things behaves a little different in *MySQL* than in other SQL servers: (This is just to ensure that *MySQL* never need to do a rollback for a SQL command). This may be a little awkward at times as column Because *MySQL* allows you to work with table types that don't support transactions, and thus can't `rollback' data, some things behave a little differently in *MySQL* than in other SQL servers. This is just to ensure that *MySQL* never need to do a rollback for a SQL command. This may be a little awkward at times as column values must be checked in the application, but this will actually give you a nice speed increase as it allows *MySQL* to do some optimizations that otherwise would be very hard to do. If you set a column to an incorrect value, *MySQL* will, instead of doing a rollback, store the `best possible value' in the column: * If you try to store a value outside the range in a numerical column, *MySQL* will instead store the smallest or biggest possible value in the column. * If you try to store a string that doesn't start with a number into a numerical column, *MySQL* will store 0 into it. * If you try to store `NULL' into a column that doesn't take `NULL' values, *MySQL* will store 0 or `''' (empty string) in it instead. (This behavior can, however, be changed with the -DDONT_USE_DEFAULT_FIELDS compile option). * *MySQL* allows you to store some wrong date values into `DATE' and `DATETIME' columns. (Like 2000-02-31 or 2000-02-00). If the date is totally wrong, *MySQL* will store the special 0000-00-00 date value in the column. * If you set an `enum' to an unsupported value, it will be set to the error value 'empty string', with numeric value 0. * If you execute a `PROCEDURE' on a query that returns an empty set, in some cases the `PROCEDURE' will not transform the columns. * Creation of a table of type `MERGE' doesn't check if the underlying tables are of compatible types. * *MySQL* can't yet handle `NaN', `-Inf' and `Inf' values in double. Using these will cause problems when trying to export and import data. We should as an intermediate solution change `NaN' to `NULL' (if possible) and `-Inf' and `Inf' to the Minimum respective maximum possible `double' value. * `LIMIT' on negative numbers are treated as big positive numbers. The following are known bugs in earlier versions of *MySQL*: * You can get a hung thread if you do a `DROP TABLE' on a table that is one among many tables that is locked with `LOCK TABLES'. * In the following case you can get a core dump: 1. Delayed insert handler has pending inserts to a table. 2. `LOCK table' with `WRITE' 3. `FLUSH TABLES' * Before *MySQL* Version 3.23.2 an `UPDATE' that updated a key with a `WHERE' on the same key may have failed because the key was used to search for records and the same row may have been found multiple times: UPDATE tbl_name SET KEY=KEY+1 WHERE KEY > 100; A workaround is to use: mysql> UPDATE tbl_name SET KEY=KEY+1 WHERE KEY+0 > 100; This will work because *MySQL* will not use index on expressions in the `WHERE' clause. * Before *MySQL* Version 3.23, all numeric types where treated as fixed-point fields. That means you had to specify how many decimals a floating-point field shall have. All results were returned with the correct number of decimals. For platform-specific bugs, see the sections about compiling and porting. How MySQL Compares to Other Databases ===================================== This section compares *MySQL* to other popular databases. This section has been written by the *MySQL* developers, so it should be read with that in mind. There are no factual errors contained in this section that we know of. If you find something which you believe to be an error, please contact us about it at . For a list of all supported limits, functions, and types, see the `crash-me' Web page at `http://www.mysql.com/information/crash-me.php'. How MySQL Compares to `mSQL' ---------------------------- *Performance* For a true comparison of speed, consult the growing *MySQL* benchmark suite. *Note MySQL Benchmarks::. Because there is no thread creation overhead, a small parser, few features, and simple security, `mSQL' should be quicker at: * Tests that perform repeated connects and disconnects, running a very simple query during each connection. * `INSERT' operations into very simple tables with few columns and keys. * `CREATE TABLE' and `DROP TABLE'. * `SELECT' on something that isn't an index. (A table scan is very easy.) Because these operations are so simple, it is hard to be better at them when you have a higher startup overhead. After the connection is established, *MySQL* should perform much better. On the other hand, *MySQL* is much faster than `mSQL' (and most other SQL implementations) on the following: * Complex `SELECT' operations. * Retrieving large results (*MySQL* has a better, faster, and safer protocol). * Tables with variable-length strings, because *MySQL* has more efficient handling and can have indexes on `VARCHAR' columns. * Handling tables with many columns. * Handling tables with large record lengths. * `SELECT' with many expressions. * `SELECT' on large tables. * Handling many connections at the same time. *MySQL* is fully multi-threaded. Each connection has its own thread, which means that no thread has to wait for another (unless a thread is modifying a table another thread wants to access). In `mSQL', once one connection is established, all others must wait until the first has finished, regardless of whether the connection is running a query that is short or long. When the first connection terminates, the next can be served, while all the others wait again, etc. * Joins. `mSQL' can become pathologically slow if you change the order of tables in a `SELECT'. In the benchmark suite, a time more than 15000 times slower than *MySQL* was seen. This is due to `mSQL''s lack of a join optimizer to order tables in the optimal order. However, if you put the tables in exactly the right order in `mSQL'2 and the `WHERE' is simple and uses index columns, the join will be relatively fast! *Note MySQL Benchmarks::. * `ORDER BY' and `GROUP BY'. * `DISTINCT'. * Using `TEXT' or `BLOB' columns. *SQL Features* * `GROUP BY' and `HAVING'. `mSQL' does not support `GROUP BY' at all. *MySQL* supports a full `GROUP BY' with both `HAVING' and the following functions: `COUNT()', `AVG()', `MIN()', `MAX()', `SUM()', and `STD()'. `COUNT(*)' is optimized to return very quickly if the `SELECT' retrieves from one table, no other columns are retrieved, and there is no `WHERE' clause. `MIN()' and `MAX()' may take string arguments. * `INSERT' and `UPDATE' with calculations. *MySQL* can do calculations in an `INSERT' or `UPDATE'. For example: mysql> UPDATE SET x=x*10+y WHERE x<20; * Aliasing. *MySQL* has column aliasing. * Qualifying column names. In *MySQL*, if a column name is unique among the tables used in a query, you do not have to use the full qualifier. * `SELECT' with functions. *MySQL* has many functions (too many to list here; see *Note Functions::). *Disk Space Efficiency* That is, how small can you make your tables? *MySQL* has very precise types, so you can create tables that take very little space. An example of a useful *MySQL* datatype is the `MEDIUMINT' that is 3 bytes long. If you have 100,000,000 records, saving even one byte per record is very important. `mSQL2' has a more limited set of column types, so it is more difficult to get small tables. *Stability* This is harder to judge objectively. For a discussion of *MySQL* stability, see *Note Stability::. We have no experience with `mSQL' stability, so we cannot say anything about that. *Price* Another important issue is the license. *MySQL* has a more flexible license than `mSQL', and is also less expensive than `mSQL'. Whichever product you choose to use, remember to at least consider paying for a license or e-mail support. (You are required to get a license if you include *MySQL* with a product that you sell, of course.) *Perl Interfaces* *MySQL* has basically the same interfaces to Perl as `mSQL' with some added features. *JDBC (Java)* *MySQL* currently has a lot of different JDBC drivers: * The mm driver: A type 4 JDBC driver by Mark Matthews . This is released under the LGPL. * The Resin driver. This is a commercial JDBC driver released under open source. `http://www.caucho.com/projects/jdbc-mysql/index.xtp' * The gwe driver: A Java interface by GWE technologies (not supported anymore). * The jms driver: An improved gwe driver by Xiaokun Kelvin ZHU (not supported anymore). * The twz driver: A type 4 JDBC driver by Terrence W. Zellers . This is commercial but is free for private and educational use (not supported anymore). The recommended driver is the mm driver. The Resin driver may also be good (at least the benchmarks looks good), but we haven't received that much information about this yet. We know that `mSQL' has a JDBC driver, but we have too little experience with it to compare. *Rate of Development* *MySQL* has a very small team of developers, but we are quite used to coding C and C++ very rapidly. Because threads, functions, `GROUP BY', and so on are still not implemented in `mSQL', it has a lot of catching up to do. To get some perspective on this, you can view the `mSQL' `HISTORY' file for the last year and compare it with the News section of the *MySQL* Reference Manual (*note News::). It should be pretty obvious which one has developed most rapidly. *Utility Programs* Both `mSQL' and *MySQL* have many interesting third-party tools. Because it is very easy to port upward (from `mSQL' to *MySQL*), almost all the interesting applications that are available for `mSQL' are also available for *MySQL*. *MySQL* comes with a simple `msql2mysql' program that fixes differences in spelling between `mSQL' and *MySQL* for the most-used C API functions. For example, it changes instances of `msqlConnect()' to `mysql_connect()'. Converting a client program from `mSQL' to *MySQL* usually takes a couple of minutes. How to Convert `mSQL' Tools for MySQL ..................................... According to our experience, it would just take a few hours to convert tools such as `msql-tcl' and `msqljava' that use the `mSQL' C API so that they work with the *MySQL* C API. The conversion procedure is: 1. Run the shell script `msql2mysql' on the source. This requires the `replace' program, which is distributed with *MySQL*. 2. Compile. 3. Fix all compiler errors. Differences between the `mSQL' C API and the *MySQL* C API are: * *MySQL* uses a `MYSQL' structure as a connection type (`mSQL' uses an `int'). * `mysql_connect()' takes a pointer to a `MYSQL' structure as a parameter. It is easy to define one globally or to use `malloc()' to get one. `mysql_connect()' also takes two parameters for specifying the user and password. You may set these to `NULL, NULL' for default use. * `mysql_error()' takes the `MYSQL' structure as a parameter. Just add the parameter to your old `msql_error()' code if you are porting old code. * *MySQL* returns an error number and a text error message for all errors. `mSQL' returns only a text error message. * Some incompatibilities exist as a result of *MySQL* supporting multiple connections to the server from the same process. How `mSQL' and MySQL Client/Server Communications Protocols Differ .................................................................. There are enough differences that it is impossible (or at least not easy) to support both. The most significant ways in which the *MySQL* protocol differs from the `mSQL' protocol are listed below: * A message buffer may contain many result rows. * The message buffers are dynamically enlarged if the query or the result is bigger than the current buffer, up to a configurable server and client limit. * All packets are numbered to catch duplicated or missing packets. * All column values are sent in ASCII. The lengths of columns and rows are sent in packed binary coding (1, 2, or 3 bytes). * *MySQL* can read in the result unbuffered (without having to store the full set in the client). * If a single read/write takes more than 30 seconds, the server closes the connection. * If a connection is idle for 8 hours, the server closes the connection. How `mSQL' 2.0 SQL Syntax Differs from MySQL ............................................ *Column types* `*MySQL*' Has the following additional types (among others; *note `CREATE TABLE': CREATE TABLE.): * `ENUM' type for one of a set of strings. * `SET' type for many of a set of strings. * `BIGINT' type for 64-bit integers. `' *MySQL* also supports the following additional type attributes: * `UNSIGNED' option for integer columns. * `ZEROFILL' option for integer columns. * `AUTO_INCREMENT' option for integer columns that are a `PRIMARY KEY'. *Note `mysql_insert_id()': mysql_insert_id. * `DEFAULT' value for all columns. `mSQL2' `mSQL' column types correspond to the *MySQL* types shown below: `mSQL' *Corresponding *MySQL* type* *type* `CHAR(len)'`CHAR(len)' `TEXT(len)'`TEXT(len)'. `len' is the maximal length. And `LIKE' works. `INT' `INT'. With many more options! `REAL' `REAL'. Or `FLOAT'. Both 4- and 8-byte versions are available. `UINT' `INT UNSIGNED' `DATE' `DATE'. Uses ANSI SQL format rather than `mSQL''s own format. `TIME' `TIME' `MONEY' `DECIMAL(12,2)'. A fixed-point value with two decimals. *Index Creation* `*MySQL*' Indexes may be specified at table creation time with the `CREATE TABLE' statement. `mSQL' Indexes must be created after the table has been created, with separate `CREATE INDEX' statements. *To Insert a Unique Identifier into a Table* `*MySQL*' Use `AUTO_INCREMENT' as a column type specifier. *Note `mysql_insert_id()': mysql_insert_id. `mSQL' Create a `SEQUENCE' on a table and select the `_seq' column. *To Obtain a Unique Identifier for a Row* `*MySQL*' Add a `PRIMARY KEY' or `UNIQUE' key to the table and use this. New in Version 3.23.11: If the `PRIMARY' or `UNIQUE' key consists of only one column and this is of type integer, one can also refer to it as `_rowid'. `mSQL' Use the `_rowid' column. Observe that `_rowid' may change over time depending on many factors. *To Get the Time a Column Was Last Modified* `*MySQL*' Add a `TIMESTAMP' column to the table. This column is automatically set to the current date and time for `INSERT' or `UPDATE' statements if you don't give the column a value or if you give it a `NULL' value. `mSQL' Use the `_timestamp' column. *`NULL' Value Comparisons* `*MySQL*' *MySQL* follows ANSI SQL, and a comparison with `NULL' is always `NULL'. `mSQL' In `mSQL', `NULL = NULL' is TRUE. You must change `=NULL' to `IS NULL' and `<>NULL' to `IS NOT NULL' when porting old code from `mSQL' to *MySQL*. *String Comparisons* `*MySQL*' Normally, string comparisons are performed in case-independent fashion with the sort order determined by the current character set (ISO-8859-1 Latin1 by default). If you don't like this, declare your columns with the `BINARY' attribute, which causes comparisons to be done according to the ASCII order used on the *MySQL* server host. `mSQL' All string comparisons are performed in case-sensitive fashion with sorting in ASCII order. *Case-insensitive Searching* `*MySQL*' `LIKE' is a case-insensitive or case-sensitive operator, depending on the columns involved. If possible, *MySQL* uses indexes if the `LIKE' argument doesn't start with a wild-card character. `mSQL' Use `CLIKE'. *Handling of Trailing Spaces* `*MySQL*' Strips all spaces at the end of `CHAR' and `VARCHAR' columns. Use a `TEXT' column if this behavior is not desired. `mSQL' Retains trailing space. *`WHERE' Clauses* `*MySQL*' *MySQL* correctly prioritizes everything (`AND' is evaluated before `OR'). To get `mSQL' behavior in *MySQL*, use parentheses (as shown in an example below). `mSQL' Evaluates everything from left to right. This means that some logical calculations with more than three arguments cannot be expressed in any way. It also means you must change some queries when you upgrade to *MySQL*. You do this easily by adding parentheses. Suppose you have the following `mSQL' query: mysql> SELECT * FROM table WHERE a=1 AND b=2 OR a=3 AND b=4; To make *MySQL* evaluate this the way that `mSQL' would, you must add parentheses: mysql> SELECT * FROM table WHERE (a=1 AND (b=2 OR (a=3 AND (b=4)))); *Access Control* `*MySQL*' Has tables to store grant (permission) options per user, host, and database. *Note Privileges::. `mSQL' Has a file `mSQL.acl' in which you can grant read/write privileges for users. `' How MySQL Compares to PostgreSQL -------------------------------- When reading the following, please note that both products are continually evolving. We at *MySQL AB* and the PostgreSQL developers are both working on making our respective database as good as possible, so we are both a serious choice to any commercial database. The following comparison is made by us at MySQL AB. We have tried to be as accurate and fair as possible, but because we don't have a full knowledge of all PostgreSQL features while we know MySQL througly, we may have got some things wrong. We will however correct these when they come to our attention. We would first like to note that `PostgreSQL' and *MySQL* are both widely used products, but with different design goals, even if we are both striving to be ANSI SQL compatible. This means that for some applications *MySQL* is more suitable and for others `PostgreSQL' is more suitable. When choosing which database to use, you should first check if the database's feature set satisfies your application. If you need speed, *MySQL* is probably your best choice. If you need some of the extra features that only `PostgreSQL' can offer, you should use `PostgreSQL'. MySQL and PostgreSQL development strategies ........................................... When adding things to MySQL we take pride to do an optimal, definite solution. The code should be so good that we shouldn't have any need to change it in the foreseeable future. We also do not like to sacrifice speed for features but instead will do our utmost to find a solution that will give maximal throughput. This means that development will take a little longer, but the end result will be well worth this. This kind of development is only possible because all server code are checked by one of a few (currently two) persons before it's included in the *MySQL* server. We at MySQL AB believe in frequent releases to be able to push out new features quickly to our users. Because of this we do a new small release about every 3 weeks, which a major branch every year. All releases are throughly tested with our testing tools on a lot of different platforms. PostgreSQL is based on a kernel with lots of contributors. In this setup it makes sense to prioritize adding a lot of new features, instead of implementing them optimally, because one can always optimize things later if there arises a need for this. Another big difference between *MySQL* and PostgreSQL is that nearly all of the code in the MySQL server are coded by developers that are employed by MySQL AB and are still working on the server code. The exceptions are the transaction engines and the regexp library. This is in sharp contrast to the PostgreSQL code where the majority of the code is coded by a big group of people with different backgrounds. It was only recently that the PostgreSQL developers announced that they current developer group had finally had time to take a look at all the code in the current PostgreSQL release. Both of the above development methods has it's own merits and drawbacks. We here at *MySQL AB* think of course that our model is better because our model gives better code consistence, more optimal and reusable code and, in our opinion, fewer bugs. Because we are the authors of the *MySQL* server code we are better able to coordinate new features and releases. Featurewise Comparison of MySQL and PostgreSQL .............................................. On the crash-me (http://www.mysql.com/information/crash-me.php) page you can find a list of those database constructs and limits that one can detect automatically with a program. Note however that a lot of the numerical limits may be changed with startup options for respective database. The above web page is however extremely useful when you want to ensure that your applications works with many different databases or when you want to convert your application from one datbase to another. *MySQL* offers the following advantages over PostgreSQL: * `MySQL' is generally much faster than PostgreSQL. *Note MySQL-PostgreSQL benchmarks::. * Because *MySQL* has a much larger user base than PostgreSQL the code is more tested and has historically been more stable than PostgreSQL. *MySQL* is the much more used in production environments than PostgreSQL, mostly thanks to that *MySQL AB*, former TCX DataKonsult AB, has provided top quality commercial support for *MySQL* from the day it was released, whereas until recently PostgreSQL was unsupported. * *MySQL* works on more platforms than PostgreSQL. *Note Which OS::. * *MySQL* works better on Windows; *MySQL* is running as a native windows application (a service on NT/Win2000/WinXP), while PostgreSQL is run under the cygwin emulation. We have heard that PostgreSQL is not yet that stable on windows but we haven't been able to verify this ourselves. * *MySQL* has more API to other languages and is supported by more programs than PostgreSQL. *Note Contrib::. * *MySQL* works on 24/7 heavy duty systems. In most circumstances you never have to run any cleanups on `MySQL'. PostgreSQL doesn't yet support 24/7 systems because you have have to run `vacuum()' once in a while to reclaim space from `UPDATE' and `DELETE' commands and to perform statistics analyzes that are critical to get good performance with PostgreSQL. Vacuum is also needed after adding a lot of new rows to a table. On a busy system with lots of changes vacuum must be run very frequently, in the worst cases even many times a day. During the `vacuum()' run, which may take hours if the database is big, the database is from a production standpoint practically dead. The PostgreSQL team has fixing this on their TODO, but we assume that this is not an easy thing to fix permanently. * A working, tested replication feature used by sites like Yahoo finance (http://finance.yahoo.com), mobile.de (http://www.mobile.de/) and Slashdot (http://www.slashdot.org). * Included in the *MySQL* distribution is included two different testing suits (`mysql-test-run' and crash-me (http://www.mysql.com/information/crash-me.php)) and a benchmark suite. The test system is actively updated with code to test each new feature and almost all repeatable bugs that comes to our attention. We test *MySQL* with these on a lot of platforms before every release. These tests are more sofisticated than anything have seen from PostgreSQL and ensures that the *MySQL* code keeps at a high standard. * There are far moore books in print on *MySQL* than on PostgreSQL. O'Reilly, Sams, Que, and New Riders are all major publishers with books about MySQL. All *MySQL* features is also documented in the *MySQL* on-line manual because when a feature is implemented, the *MySQL* developers are required to document it before it's included in the source. * *MySQL* has supports more of the standard ODBC functions than `PostgreSQL'. * *MySQL* has a much more sophisticated `ALTER TABLE'. * *MySQL* has support for tables without transactions for applications that need all speed they can get. The tables may be memory based,`HEAP' tables or disk based `MyISAM'. *Note Table types::. * *MySQL* has support for 3 different table handles that support transactions (`BDB' and `InnoDB'). Because every transaction engine performs differently under different conditions, this gives the application writer more options to find an optimal solution for his/her setup. *Note Table types::. * `MERGE' tables gives you a unique way to instantly make a view over a set of identical tables and use these as one. This is perfectly for systems where you have log files that you order for example by month. *Note MERGE::. * The option to compress read-only tables, but still have direct access to the rows in the table, gives you better performance by minimizing disk reads. This is very useful when you are archiving things.*Note myisampack::. * *MySQL* has internal support for text search. *Note Fulltext Search::. * You can access many databases from the same connection (depending of course on your privileges). * *MySQL* is coded from the start with multi-threading while PostgreSQL uses processes. Because context switching and access to common storage areas is much faster between threads, than are separate processes, this gives *MySQL* a big speed advantage in multi-user applications and also makes it easier for *MySQL* to take full advantage of symmetric multiprocessor systems (SMP). * *MySQL* has a much more sophisticated privilege system than PostgreSQL. While PostgreSQL only supports `INSERT', `SELECT', `update/delete' grants per user on a database or a table *MySQL* allows you to define a full set of different privileges on database, table and columns level. *MySQL* also allows you to specify the privilege on host+user combinations. *Note GRANT::. * *MySQL* supports a compressed server/client protocol which improves performance over slow links. * *MySQL* employs the table handler concept and is the only relational database we know of built around this concept. This allows different low level table types to be swapped into the SQL engine, each table type optimized for a different performance characteristics. * All `MySQL' table types (except *InnoDB*) are implemented as files (ie: one table per file), which makes it really easy to backup, move, delete and even symlink databases and tables when the server is down. * Tools to repair and optimize *MyISAM* tables (the most common *MySQL* table type). A repair tool is only needed when a physical corruption of a data file happens, usually from a hardware failure. It allows a majority of the data to be recovered. * Upgrading *MySQL* is painless. When you are upgrading *MySQL*, you don't need to dump/restore your data, as you have to do with most PostgreSQL upgrades. Drawbacks with *MySQL* compared to PostgreSQL: * The transaction support in *MySQL* is not yet as well tested as PostgreSQL's system. * Because *MySQL* uses threads, which are still a moving target on many OS, one must either use binaries from `http://www.mysql.com/downloads' or carefully follow our instructions on `http://www.mysql.com/doc/I/n/Installing_source.html' to get an optimal binary that works in all cases. * Table locking, as used by the non-transactional `MyISAM' tables, is in many cases faster than page locks, row locks or versioning. The drawback however is that if one doesn't take into account how table locks works, a single long-running query can block a table for updates for a long time. This can usable be avoided when designing the application. If not, one can always switch the trouble table to use one of the transactional table types. *Note Table locking::. * With UDF (user defined functions) one can extend *MySQL* with both normal SQL functions and aggregates, but this is not as easy or as flexible as in PostgreSQL. *Note Adding functions::. * Updates and deletes that goes over multiple tables is harder to do in *MySQL*. (Will be fixed in *MySQL* 4.0 with multi-table `DELETE' and multi-table `UPDATE' and in *MySQL* 4.1 with `SUB-SELECT') PostgreSQL offers currently the following advantages over *MySQL*: Note that because we know the *MySQL* road map, we have included in the following table the version when *MySQL* should support this feature. Unfortunately we couldn't do this for previous comparison, because we don't know the PostgreSQL roadmap. *Feature* *MySQL version* Subselects 4.1 Foreign keys 4.0 and 4.1 Views. 4.2 Stored procedures in multiple languages 4.1 Extensible type system. Not planed Unions 4.0. Full join. 4.0 or 4.1. Triggers. 4.1 Constrainst 4.1 Cursors 4.1 or 4.2 Extensible index types like R-trees R-trees are planned to 4.2 Inherited tables Not planned Other reasons to use PostgreSQL: * Standard usage is in PostgreSQL closer to ANSI SQL in some cases. * One can get speed up PostgreSQL by coding things as stored procedures. * Bigger team of developers that contributes to the server. Drawbacks with PostgreSQL compared to *MySQL*: * `Vaccum()' makes PostgreSQL hard to use in a 24/7 environment. * Only transactional tables. * Much slower insert/delete/update. For a complete list of drawbacks, you should also examine the first table in this section. Benchmarking MySQL and PostgreSQL ................................. The only open source benchmark, that we know of, that can be used to benchmark *MySQL* and PostgreSQL (and other databases) is our own. It can be found at: `http://www.mysql.com/information/benchmarks.html'. We have many times asked the PostgreSQL developers and some PostgreSQL users to help us extend this benchmark to make the definitive benchmark for databases, but unfortunately we haven't got any feedback for this. We, the *MySQL* developers, have because of this spent a lot of hours to get maximum performance from PostgreSQL for the benchmarks, but because we don't know PostgreSQL intimately we are sure that there are things that we have missed. We have on the benchmark page documented exactly how we did run the benchmark so that it should be easy for anyone to repeat and verify our results. The benchmarks are usually run with and without the `--fast' option. When run with `--fast' we are trying to use every trick the server can do to get the code to execute as fast as possible. The idea is that the normal run should show how the server would work in a default setup and the `--fast' run shows how the server would do if the application developer would use extensions in the server to make his application run faster. When running with PostgreSQL and `--fast' we do a `vacuum()' between after every major table update and drop table to make the database in perfect shape for the following selects. The time for vacuum() is measured separately. When running with PostgreSQL 7.1.1 we could however not run with `--fast' because during the insert test, the postmaster (the PostgreSQL deamon) died and the database was so corrupted that it was impossible to restart postmaster. (The details about the machine we run the benchmark can be found on the benchmark page). After this happened twice, we decided to postpone the `--fast' test until next PostgreSQL release. Before going to the other benchmarks we know of, We would like to give some background to benchmarks: It's very easy to write a test that shows ANY database to be best database in the world, by just restricting the test to something the database is very good at and not test anything that the database is not good at; If one after this publish the result with a single figure things is even easier. This would be like we would measure the speed of *MySQL* compared to PostgreSQL by looking at the summary time of the MySQL benchmarks on our web page. Based on this *MySQL* would be more than 40 times faster than PostgreSQL, something that is of course not true. We could make things even worse by just taking the test where PostgreSQL performs worst and claim that *MySQL* is more than 2000 times faster than PostgreSQL. The case is that *MySQL* does a lot of optimizations that PostgreSQL doesn't do and the other way around. An SQL optimizer is a very complex thing and a company could spend years on just making the optimizer faster and faster. When looking at the benchmark results you should look for things that you do in your application and just use these results to decide which database would be best suited for your application. The benchmark results also shows things a particular database is not good at and should give you a notion about things to avoid and what you may have to do in other ways. We know of two benchmark tests that claims that PostgreSQL performers better than *MySQL*. These both where multi-user tests, a test that we here at *MySQL AB* haven't had time to write and include in the benchmark suite, mainly because it's a big task to do this in a manner that is fair against all databases. One is the benchmark paid for by Great Bridge (http://www.greatbridge.com/about/press.php?content_id=4). This is the worst benchmark we have ever seen anyone ever conduct. This was not only tuned to only test what PostgreSQL is absolutely best at, it was also totally unfair against every other database involved in the test. *NOTE*: We know that not even some of the main PostgreSQL developers did like the way Great Bridge conducted the benchmark, so we don't blame them for the way the benchmark was made. This benchmark has been condemned in a lot of postings and newsgroups so we will here just shortly repeat some things that where wrong with it. * The tests where run with an expensive commercial tool, that makes it impossible for an open source company like us to verify the benchmarks, or even check how the benchmark where really done. The tool is not even a true benchmark tool, but a application/setup testing tool. To refer this as STANDARD benchmark tool is to stretch the truth a long way. * Great Bridge admitted that they had optimized the PostgreSQL database (with vacuum() before the test) and tuned the startup for the tests, something they hadn't done for any of the other databases involved. To say "This process optimizes indexes and frees up disk space a bit. The optimized indexes boost performance by some margin". Our benchmarks clearly indicates that the difference in running a lot of selects on a database with and without vacuum() can easily differ by a factor of 10. * The test results where also strange; The AS3AP test documentation mentions that the test does: "selections, simple joins, projections, aggregates, one-tuple updates, and bulk updates" PostgreSQL is good at doing selects and joins (especially after a vacuum()), but doesn't perform as well on inserts/updates; The benchmarks seem to indicate that only SELECTs where done (or very few updates) . This could easily explain they good results for PostgreSQL in this test. The bad results for MySQL will be obvious a bit down in this document. * They did run the so called benchmark from a Windows machine against a Linux machine over ODBC, a setup that no normal database user would ever do when running a heavy multi-user application. This tested more the ODBC driver and the Windows protocol used between the clients than the database itself. * When running the database against Oracle and MS-SQL (Great Bridge has indirectly indicated that the databases they used in the test), they didn't use the native protocol but instead ODBC. Anyone that has ever used Oracle, knows that all real application uses the native interface instead of ODBC. Doing a test through ODBC and claiming that the results had anything to do with using the database for real can't be regarded as fair play. They should have done two tests with and without ODBC to provide the right facts (after having got experts to tune all involved databases of course). * They refer to the TPC-C tests, but doesn't anywhere mention that the tests they did where not a true TPC-C test and they where not even allowed to call it a TPC-C test. A TPC-C test can only be conducted by the rules approved by the TPC-council (http://www.tpc.org). Great Bridge didn't do that. By doing this they have both violated the TPC trademark and miscredited their own benchmarks. The rules set by the TPC-council are very strict to ensure that no one can produce false results or make unprovable statements. Apparently Great Bridge wasn't interested in doing this. * After the first test, we contacted Great Bridge and mentioned to them some of the obvious mistakes they had done with *MySQL*; Running with a debug version of our ODBC driver, running on a Linux system that wasn't optimized for threads, using an old MySQL version when there was a recommended newer one available, not starting *MySQL* with the right options for heavy multi-user use (the default installation of MySQL is tuned for minimal resource use). Great Bridge did run a new test, with our optimized ODBC driver and with better startup options for MySQL, but refused to either use our updated glibc library or our standard binary (used by 80% of our users), which was statically linked with a fixed glibc library. According to what we know, Great Bridge did nothing to ensure that the other databases where setup correctly to run good in their test environment. We are sure however that they didn't contact Oracle or Microsoft to ask for their advice in this matter ;) * The benchmark was paid for by Great Bridge, and they decided to publish only partial chosen results (instead of publishing it all). Tim Perdue, a long time PostgreSQL fan and a reluctant MySQL user published a comparison on phpbuider (http://www.phpbuilder.com/columns/tim20001112.php3). When we got aware of the comparison, we phoned Tim Perdue about this because there was a lot of strange things in his results. For example, he claimed that MySQL had a problem with five users in his tests, when we know that there are users with similar machines as his that are using MySQL with 2000 simultaneous connections doing 400 queries per second (In this case the limit was the web bandwidth, not the database). It sounded like he was using a Linux kernel that either had some problems with many threads (Linux kernels before 2.4 had a problem with this but we have documented how to fix this and Tim should be aware of this problem). The other possible problem could have been an old glibc library and that Tim didn't use a MySQL binary from our site, which is linked with a corrected glibc library, but had compiled a version of his own with. In any of the above cases, the symptom would have been exactly what Tim had measured. We asked Tim if we could get access to his data so that we could repeat the benchmark and if he could check the MySQL version on the machine to find out what was wrong and he promised to come back to us about this. He has not done that yet. Because of this we can't put any trust in this benchmark either :( Conclusion: The only benchmarks that exist today that anyone can download and run against *MySQL*and PostgreSQL is the MySQL benchmarks. We here at *MySQL* believe that open source databases should be tested with open source tools! This is the only way to ensure that no one does tests that nobody can reproduce and use this to claim that a database is better than another. Without knowing all the facts it's impossible to answer the claims of the tester. The thing we find strange is that every test we have seen about PostgreSQL, that is impossible to reproduce, claims that PostgreSQL is better in most cases while our tests, which anyone can reproduce, clearly shows otherwise. With this we don't want to say that PostgreSQL isn't good at many things (It is!) We would just like to see a fair test where they are very good so that we could get some friendly competition going! For more information about our benchmarks suite see *Note MySQL Benchmarks::. We are working on an even better benchmark suite, including much better documentation of what the individual tests really do and how to add more tests to the suite. MySQL and the future (The TODO) =============================== This appendix lists the features that we plan to implement in *MySQL*. Everything in this list is approximately in the order it will be done. If you want to affect the priority order, please register a license or support us and tell us what you want to have done more quickly. *Note Licensing and Support::. The plan is that we in the future will support the full ANSI SQL99 standard, but with a lot of useful extensions. The challenge is to do this without sacrifying the speed or compromise the code. Things that should be in 4.0 ---------------------------- We plan to make *MySQL* Version 4.0 a "quick" release where we only add some new stuff to enable others to help us with developing new features into Version 4.1. The *MySQL* 4.0 version should only take us about a month to make after which we want to stabilize it and start working on Version 4.1. Version 4.0 should have the following new features: The news section for 4.0 includes a list of the features we have already implemented in the 4.0 tree. *Note News-4.0.x::. * New table definition file format (`.frm' files) This will enable us to not run out of bits when adding more table options. One will still be able to use the old `.frm' file format with 4.0. All newly created tables will, however, use the new format. The new file format will enable us to add new column types, more options for keys and `FOREIGN KEY' support. * `mysqld' as a library. This will have the same interface as the standard *MySQL* client (with an extra function to just set up startup parameters) but will be faster (no TCP/IP or socket overhead), smaller and much easier to use for embedded products. One will be able to define at link time if one wants to use the client/server model or a stand-alone application just by defining which library to link with. The `mysqld' will support all standard *MySQL* features and one can use it in a threaded client to run different queries in each thread. * Replication should work with `RAND()' and user variables `@var'. * Online backup with very low performance penalty. The online backup will make it easy to add a new replication slave without taking down the master. * `DELETE FROM table_name' will return the number of deleted rows. For fast execution one should use `TRUNCATE table_name'. * Allow `DELETE' on `MyISAM' tables to use the record cache. To do this, we need to update the threads record cache when we update the `.MYD' file. * Better replication. * More functions for full-text search. *Note Fulltext Features to Appear in MySQL 4.0::. * Character set casts and syntax for handling multiple character sets. * Allow users to change startup options without taking down the server. * Help for all commands from the client. * Secure connections (with SSL). * Extend the optimizer to be able to optimize some `ORDER BY key_name DESC' queries. * `SHOW COLUMNS FROM table_name' (used by `mysql' client to allow expansions of column names) should not open the table, but only the definition file. This will require less memory and be much faster. * New key cache * When using `SET CHARACTER SET' we should translate the whole query at once and not only strings. This will enable users to use the translated characters in database, table and column names. * Add a portable interface over `gethostbyaddr_r()' so that we can change `ip_to_hostname()' to not block other threads while doing DNS lookups. * Add `record_in_range()' method to `MERGE' tables to be able to choose the right index when there is many to choose from. We should also extend the info interface to get the key distribution for each index, of `analyze' is run on all sub tables. * `SET SQL_DEFAULT_TABLE_TYPE=[MyISAM | INNODB | BDB | HEAP]'. Things that must be done in the real near future ------------------------------------------------ * Fail safe replication. * Subqueries. `select id from t where grp in (select grp from g where u > 100)' * Derived tables. select a.col1, b.col2 from (select max(col1) as col1 from root_table ) a, other_table b where a.col1=b.col1 This could be done by automatically creating temporary tables for the derived tables for the duration of the query. * Add `PREPARE' of statements and sending of parameters to `mysqld'. * Extend the server/client protocol to support warnings. * Add options to the server/protocol protocol to get progress notes for long running commands. * Add database and real table name (in case of alias) to the MYSQL_FIELD structure. * Don't allow more than a defined number of threads to run MyISAM recover at the same time. * Change `INSERT ... SELECT' to optionally use concurrent inserts. * Implement `RENAME DATABASE'. To make this safe for all table handlers, it should work as follows: * Create the new database. * For every table do a rename of the table to another database, as we do with the `RENAME' command. * Drop the old database. * Return the original field types() when doing `SELECT MIN(column) ... GROUP BY'. * Multiple result sets. * Change the protocol to allow binary transfer of values. To do this efficiently, we need to add an API to allow binding of variables. * Make it possible to specify `long_query_time' with a granularity in microseconds. * Add a configurable prompt to the `mysql' command line client, with options like database in use, time and date... * Add range checking to `MERGE' tables. * Link the `myisampack' code into the server. * Port of *MySQL* to BeOS. * Port of the *MySQL* clients to LynxOS. * Add a temporary key buffer cache during `INSERT/DELETE/UPDATE' so that we can gracefully recover if the index file gets full. * If you perform an `ALTER TABLE' on a table that is symlinked to another disk, create temporary tables on this disk. * Implement a `DATE/DATETIME' type that handles time zone information properly, so that dealing with dates in different time zones is easier. * FreeBSD and MIT-pthreads; Do sleeping threads take CPU? * Check if locked threads take any CPU. * Fix configure so that one can compile all libraries (like `MyISAM') without threads. * Add an option to periodically flush key pages for tables with delayed keys if they haven't been used in a while. * Allow join on key parts (optimization issue). * `INSERT SQL_CONCURRENT' and `mysqld --concurrent-insert' to do a concurrent insert at the end of the file if the file is read-locked. * Remember `FOREIGN' key definitions in the `.frm' file. * Cascading `DELETE' * Server side cursors. * Check if `lockd' works with modern Linux kernels; If not, we have to fix `lockd'! To test this, start `mysqld' with `--enable-locking' and run the different fork* test suits. They shouldn't give any errors if `lockd' works. * Allow SQL variables in `LIMIT', like in `LIMIT @a,@b'. * Allow update of variables in `UPDATE' statements. For example: `UPDATE TABLE foo SET @a=a+b,a=@a, b=@a+c' * Change when user variables are updated so that one can use them with `GROUP BY', as in the following example: `SELECT id, @a:=count(*), sum(sum_col)/@a FROM table_name GROUP BY id'. * Don't add automatic `DEFAULT' values to columns. Give an error when using an `INSERT' that doesn't contain a column that doesn't have a `DEFAULT'. * Caching of queries and results. This should be done as a separated module that examines each query and if this is query is in the cache the cached result should be returned. When one updates a table one should remove as few queries as possible from the cache. This should give a big speed bost on machines with much RAM where queries are often repeated (like WWW applications). One idea would be to only cache queries of type: `SELECT CACHED ...' * Fix `libmysql.c' to allow two `mysql_query()' commands in a row without reading results or give a nice error message when one does this. * Optimize `BIT' type to take 1 bit (now `BIT' takes 1 char). * Check why MIT-pthreads `ctime()' doesn't work on some FreeBSD systems. * Add an `IMAGE' option to `LOAD DATA INFILE' to not update `TIMESTAMP' and `AUTO_INCREMENT' fields. * Added `LOAD DATE INFILE.. UPDATE' syntax. * For tables with primary keys, if the data contains the primary key, entries matching that primary key are updated from the remainder of the columns. However, columns MISSING from the incoming data feed are not touched. * For tables tables with primary keys that are missing some part of the key in the incoming data stream, or that have no primary key, the feed is treated as a `LOAD DATA INFILE ... REPLACE INTO' is now. * Make `LOAD DATA INFILE' understand syntax like: LOAD DATA INFILE 'file_name.txt' INTO TABLE tbl_name TEXT_FIELDS (text_field1, text_field2, text_field3) SET table_field1=concatenate(text_field1, text_field2), table_field3=23 IGNORE text_field3 This can be used to skip over extra columns in the text file, or update columns based on expressions of the read data... * `LOAD DATA INFILE 'file_name' INTO TABLE 'table_name' ERRORS TO err_table_name' This would cause any errors and warnings to be logged into the err_table_name table. That table would have a structure like: line_number - line number in data file error_message - the error/warning message and maybe data_line - the line from the data file * Add true `VARCHAR' support (There is already support for this in MyISAM). * Automatic output from `mysql' to netscape. * `LOCK DATABASES'. (with various options) * Change sort to allocate memory in "hunks" to get better memory utilization. * `DECIMAL' and `NUMERIC' types can't read exponential numbers; `Field_decimal::store(const char *from,uint len)' must be recoded to fix this. * Fix `mysql.cc' to do fewer `malloc()' calls when hashing field names. * Functions: ADD_TO_SET(value,set) and REMOVE_FROM_SET(value,set) * Add use of `t1 JOIN t2 ON ...' and `t1 JOIN t2 USING ...' Currently, you can only use this syntax with `LEFT JOIN'. * Add full support for `unsigned long long' type. * Many more variables for `show status'. Counts for: `INSERT'/`DELETE'/`UPDATE' statements. Records reads and updated. Selects on 1 table and selects with joins. Mean number of tables in select. Number of `ORDER BY' and `GROUP BY' queries. * If you abort `mysql' in the middle of a query, you should open another connection and kill the old running query. Alternatively, an attempt should be made to detect this in the server. * Add a handler interface for table information so you can use it as a system table. This would be a bit slow if you requested information about all tables, but very flexible. `SHOW INFO FROM tbl_name' for basic table information should be implemented. * Add support for UNICODE. * `NATURAL JOIN' and `UNION JOIN' * Allow `select a from crash_me left join crash_me2 using (a)'; In this case a is assumed to come from the crash_me table. * Fix that `ON' and `USING' works with the `JOIN' and `INNER JOIN' join types. * Oracle like `CONNECT BY PRIOR ...' to search hierarchy structures. * `RENAME DATABASE' * `mysqladmin copy database new-database'. - Requires COPY command to be added to `mysqld' * Processlist should show number of queries/thread. * `SHOW HOSTS' for printing information about the hostname cache. * `DELETE' and `REPLACE' options to the `UPDATE' statement (this will delete rows when one gets a duplicate key error while updating). * Change the format of `DATETIME' to store fractions of seconds. * Add all missing ANSI92 and ODBC 3.0 types. * Change table names from empty strings to `NULL' for calculated columns. * Don't use 'Item_copy_string' on numerical values to avoid number->string->number conversion in case of: `SELECT COUNT(*)*(id+0) FROM table_name GROUP BY id' * Make it possible to use the new GNU regexp library instead of the current one (The GNU library should be much faster than the old one). * Change that `ALTER TABLE' doesn't abort clients that executes `INSERT DELAYED'. * Fix that when columns referenced in an `UPDATE' clause contains the old values before the update started. * `myisamchk', `REPAIR' and `OPTIMIZE TABLE' should be able to handle cases where the data and/or index files are symbolic links. * Add simulation of `pread()'/`pwrite()' on Windows to enable concurrent inserts. * A logfile analyzer that could parsed out information about which tables are hit most often, how often multi-table joins are executed, etc. It should help users identify areas or table design that could be optimized to execute much more efficient queries. * Add `SUM(DISTINCT)' * Add `ANY()',`EVERY()' and `SOME()' group functions. In ANSI SQL these only works on boolean columns, but we can extend these to work on any columns/expressions by applying: value == 0 -> FALSE and value <> 0 -> TRUE. * Fix that the type for `MAX(column)' is the same as the column type. create table t1 (a DATE); insert into t1 values (now()); create table t2 select max(a) from t1; show columns from t2; * Come up with a nice syntax for a statement that will `UPDATE' the row if it exists and `INSERT' a new row if the row didn't exist. (Like `REPLACE' works with `INSERT' / `DELETE') Things that have to be done sometime ------------------------------------ * Implement function: `get_changed_tables(timeout,table1,table2,...)' * Atomic multi-table updates, eg `update items,month set items.price=month.price where items.id=month.id;'; * Change reading through tables to use memmap when possible. Now only compressed tables use memmap. * Add a new privilege *'Show_priv'* for `SHOW' commands. * Make the automatic timestamp code nicer. Add timestamps to the update log with `SET TIMESTAMP=#;' * Use read/write mutex in some places to get more speed. * Full foreign key support. One probably wants to implement a procedural language first. * Simple views (first on one table, later on any expression). * Automatically close some tables if a table, temporary table or temporary files gets error 23 (not enough open files). * When one finds a field=#, change all occurrences of field to #. Now this is only done for some simple cases. * Change all const expressions with calculated expressions if possible. * Optimize key = expression. At the moment only key = field or key = constant are optimized. * Join some of the copy functions for nicer code. * Change `sql_yacc.yy' to an inline parser to reduce its size and get better error messages (5 days). * Change the parser to use only one rule per different number of arguments in function. * Use of full calculation names in the order part. (For ACCESS97) * `UNION', `MINUS', `INTERSECT' and `FULL OUTER JOIN'. (Currently only `LEFT OUTER JOIN' is supported) * Allow `UNIQUE' on fields that can be `NULL'. * `SQL_OPTION MAX_SELECT_TIME=#' to put a time limit on a query. * Make the update log to a database. * Negative `LIMIT' to retrieve data from the end. * Alarm around client connect/read/write functions. * Please note the changes to `safe_mysqld': according to FSSTND (which Debian tries to follow) PID files should go into `/var/run/.pid' and log files into `/var/log'. It would be nice if you could put the "DATADIR" in the first declaration of "pidfile" and "log", so the placement of these files can be changed with a single statement. * Allow a client to request logging. * Add use of `zlib()' for `gzip'-ed files to `LOAD DATA INFILE'. * Fix sorting and grouping of `BLOB' columns (partly solved now). * Stored procedures. This is currently not regarded to be very important as stored procedures are not very standardized yet. Another problem is that true stored procedures make it much harder for the optimizer and in many cases the result is slower than before We will, on the other hand, add a simple (atomic) update language that can be used to write loops and such in the *MySQL* server. * Change to use semaphores when counting threads. One should first implement a semaphore library to MIT-pthreads. * Don't assign a new `AUTO_INCREMENT' value when one sets a column to 0. Use `NULL' instead. * Add full support for `JOIN' with parentheses. * As an alternative for one thread / connection manage a pool of threads to handle the queries. * Allow one to get more than one lock with `GET_LOCK'. When doing this, one must also handle the possible deadlocks this change will introduce. Time is given according to amount of work, not real time. Some things we don't have any plans to do ----------------------------------------- * Nothing; In the long run we plan to be fully ANSI 92 / ANSI 99 compliant. MySQL Installation ****************** This chapter describes how to obtain and install *MySQL*: * For a list of sites from which you can obtain *MySQL*, see *Note Getting *MySQL*: Getting MySQL. * To see which platforms are supported, see *Note Which OS::. Please note that not all supported system are equally good for running *MySQL* on them. On some it is much more robust and efficient than others - see *Note Which OS:: for details. * Several versions of *MySQL* are available in both binary and source distributions. We also provide public access to our current source tree for those who want to see our most recent developments and help us test new code. To determine which version and type of distribution you should use, see *Note Which version::. When in doubt, use the binary distribution. * Installation instructions for binary and source distributions are described in *Note Installing binary:: and *Note Installing source::. Each set of instructions includes a section on system-specific problems you may run into. * For post-installation procedures, see *Note Post-installation::. These procedures apply whether you install *MySQL* using a binary or source distribution. Quick Standard Installation of MySQL ==================================== Installing MySQL on Linux ------------------------- The recommended way to install *MySQL* on Linux is by using an RPM file. The *MySQL* RPMs are currently being built on a RedHat Version 6.2 system but should work on other versions of Linux that support `rpm' and use `glibc'. If you have problems with an RPM file, for example, if you receive the error "`Sorry, the host 'xxxx' could not be looked up'", see *Note Binary notes-Linux::. The RPM files you may want to use are: * `MySQL-VERSION.i386.rpm' The *MySQL* server. You will need this unless you only want to connect to a *MySQL* server running on another machine. * `MySQL-client-VERSION.i386.rpm' The standard *MySQL* client programs. You probably always want to install this package. * `MySQL-bench-VERSION.i386.rpm' Tests and benchmarks. Requires Perl and msql-mysql-modules RPMs. * `MySQL-devel-VERSION.i386.rpm' Libraries and include files needed if you want to compile other *MySQL* clients, such as the Perl modules. * `MySQL-VERSION.src.rpm' This contains the source code for all of the above packages. It can also be used to try to build RPMs for other architectures (for example, Alpha or SPARC). To see all files in an RPM package, run: shell> rpm -qpl MySQL-VERSION.i386.rpm To perform a standard minimal installation, run: shell> rpm -i MySQL-VERSION.i386.rpm MySQL-client-VERSION.i386.rpm To install just the client package, run: shell> rpm -i MySQL-client-VERSION.i386.rpm The RPM places data in `/var/lib/mysql'. The RPM also creates the appropriate entries in `/etc/rc.d/' to start the server automatically at boot time. (This means that if you have performed a previous installation, you may want to make a copy of your previously installed *MySQL* startup file if you made any changes to it, so you don't lose your changes.) After installing the RPM file(s), the `mysqld' daemon should be running and you should now be able to start using *MySQL*. *Note Post-installation::. If something goes wrong, you can find more information in the binary installation chapter. *Note Installing binary::. Installing MySQL on Windows --------------------------- The following instructions apply to precompiled binary distributions. If you download a source distribution, you will have to compile and install it yourself. If you don't have a copy of the *MySQL* distribution, you should first download one from `http://www.mysql.com/downloads/mysql-3.23.html'. If you plan to connect to *MySQL* from some other program, you will probably also need the *MyODBC* driver. You can find this at the *MyODBC* download page (`http://www.mysql.com/downloads/api-myodbc.html'). To install either distribution, unzip it in some empty directory and run the `Setup.exe' program. By default, *MySQL*-Windows is configured to be installed in `C:\mysql'. If you want to install *MySQL* elsewhere, install it in `C:\mysql' first, then move the installation to where you want it. If you do move *MySQL*, you must indicate where everything is located by supplying a `--basedir' option when you start the server. For example, if you have moved the *MySQL* distribution to `D:\programs\mysql', you must start `mysqld' like this: C:\> D:\programs\mysql\bin\mysqld --basedir D:\programs\mysql Use `mysqld --help' to display all the options that `mysqld' understands! With all newer *MySQL* versions, you can also create a `C:\my.cnf' file that holds any default options for the *MySQL* server. Copy the file `\mysql\my-xxxxx.cnf' to `C:\my.cnf' and edit it to suit your setup. Note that you should specify all paths with `/' instead of `\'. If you use `\', you need to specify it twice, because `\' is the escape character in *MySQL*. *Note Option files::. Starting with *MySQL* 3.23.38, the Windows distribution includes both the normal and the *MySQL-Max* binaries. The main benefit of using the normal `mysqld.exe' binary is that it's a little faster and uses less resources. Here is a list of the different *MySQL* servers you can use: `mysqld' Compiled with full debugging and automatic memory allocation checking, symbolic links, BDB and InnoDB tables. `mysqld-opt' Optimized binary with no support for transactional tables. `mysqld-nt' Optimized binary for NT with support for named pipes. You can run this version on Win98, but in this case no named pipes are created and you must have TCP/IP installed. `mysqld-max' Optimized binary with support for symbolic links, BDB and InnoDB tables. `mysqld-max-nt' Like `mysqld-max', but compiled with support for named pipes. All of the above binaries are optimized for the Pentium Pro processor but should work on any Intel processor >= i386. NOTE: If you want to use InnoDB tables, there are certain startup options that must be specified in your `my.ini' file! *Note InnoDB start::. General Installation Issues =========================== How to Get MySQL ---------------- Check the *MySQL* home page (http://www.mysql.com/) for information about the current version and for downloading instructions. Our main download mirror is located at: `http://download.sourceforge.net/mirrors/mysql/' If you are interested in becoming a *MySQL* mirror site, you may anonymously rsync with: `rsync://download.sourceforge.net/mysql/'. Please send e-mail to notifying us of your mirror to be added to the list below. If you have problems downloading from our main site, try using one of the mirrors listed below. Please report bad or out-of-date mirrors to . *Europe:* * Austria [Univ. of Technology/Vienna] WWW (http://gd.tuwien.ac.at/db/mysql/) FTP (ftp://gd.tuwien.ac.at/db/mysql/) * Bulgaria [online.bg/Sofia] WWW (http://mysql.online.bg/) FTP (ftp://mysql.online.bg/) * Czech Republic [Masaryk University in Brno] WWW (http://mysql.linux.cz/index.html) FTP (ftp://ftp.fi.muni.cz/pub/mysql/) * Czech Republic [www.sopik.cz] WWW (http://www.mysql.cz/) * Czech Republic [www.gin.cz] WWW (http://mysql.gin.cz/) FTP (ftp://ftp.gin.cz/pub/MIRRORS/www.mysql.com/) * Denmark [Borsen] WWW (http://mysql.borsen.dk/) * Denmark [SunSITE] WWW (http://SunSITE.auc.dk/mysql/) FTP (ftp://SunSITE.auc.dk/pub/databases/mysql/) * Estonia [OKinteractive] WWW (http://mysql.mirror.ok.ee) * France [mtesa.net] WWW (http://mysql.mtesa.net/) * France [fastorama.com, Chatenois] WWW (http://mysql.fastorama.com/) FTP (ftp://ftp.fastorama.com/unix/mysql/) * Finland [tonnikala.net] WWW (http://mysql.tonnikala.org/) * Germany [Kernelnotes.de, Bonn] WWW (http://www.kernelnotes.de/mysql/) FTP (ftp://ftp.kernelnotes.de/pub/mirror/mysql.org/) * Germany [Wolfenbuettel] WWW (http://www.fh-wolfenbuettel.de/ftp/pub/database/mysql/) FTP (ftp://ftp.fh-wolfenbuettel.de/pub/database/mysql/) * Greece [NTUA, Athens] WWW (http://www.ntua.gr/mysql/) FTP (ftp://ftp.ntua.gr/pub/databases/mysql/) * Hungary [Xenia] WWW (http://mysql.sote.hu/) FTP (ftp://xenia.sote.hu/pub/mirrors/www.mysql.com/) * Hungary [TiszaneT] WWW (http://mysql.tiszanet.hu/) FTP (ftp://mysql.tiszanet.hu/pub/mirrors/mysql/) * Hungary [stop.hu] WWW (http://mysql.mirror.stop.hu/) * Iceland [GM] WWW (http://mysql.gm.is/) FTP (ftp://ftp.gm.is/pub/mysql/) * Italy [feelinglinux.com] WWW (http://mysql.feelinglinux.com/) * Italy [Teta Srl] WWW (http://www.teta.it/mysql/) * Italy [tzone.it] WWW (http://mysql.tzone.it/) * Ireland [Esat Net] WWW (http://ftp.esat.net/mirrors/download.sourceforge.net/pub/mirrors/mysql/) FTP (ftp://ftp.esat.net/mirrors/download.sourceforge.net/pub/mirrors/mysql/) * Latvia [linux.lv] FTP (ftp://ftp.linux.lv/pub/software/mysql/) * Netherlands [Silverpoint] WWW (http://mysql.silverpoint.nl/) * Netherlands [Widexs BV] WWW (http://mysql.widexs.nl/) FTP (ftp://mysql.widexs.nl/pub/mysql/) * Netherlands [ProServe] WWW (http://mysql.proserve.nl/) * Poland [Sunsite] WWW (http://sunsite.icm.edu.pl/mysql/) FTP (ftp://sunsite.icm.edu.pl/pub/unix/mysql/) * Poland [ncservice.com/Gdansk] WWW (http://mysql.service.net.pl/) * Portugal [Netc] WWW (http://ftp.netc.pt/pub/mysql/) FTP (ftp://ftp.netc.pt/pub/mysql/) * Romania [roedu.net/Bucharest] FTP (ftp://ftp.roedu.net/pub/mirrors/ftp.mysql.com/) * Russia [DirectNet] WWW (http://mysql.directnet.ru/) FTP (ftp://ftp.dn.ru/pub/MySQL/) * Russia [Scientific Center/Chernogolovka] FTP (ftp://ftp.chg.ru/pub/databases/mysql/) * Switzerland [Sunsite] WWW (http://sunsite.cnlab-switch.ch/ftp/mirror/mysql/) FTP (ftp://sunsite.cnlab-switch.ch/mirror/mysql/) * UK [Omnipotent/UK] WWW (http://mysql.omnipotent.net/) FTP (ftp://mysql.omnipotent.net/) * UK [PLiG/UK] WWW (http://ftp.plig.org/pub/mysql/) FTP (ftp://ftp.plig.org/pub/mysql/) * Ukraine [PACO] WWW (http://mysql.paco.net.ua) FTP (ftp://mysql.paco.net.ua/) * Ukraine [ISP Alkar Teleport/Dnepropetrovsk] WWW (http://mysql.dp.ua/) * Yugoslavia [bolex.co.yu] WWW (http://mysql.boa.org.yu/) FTP (ftp://ftp.linux.org.yu/pub/MySQL/) *North America:* * Canada [Tryc] WWW (http://web.tryc.on.ca/mysql/) * USA [Hurricane Electric/San Jose] WWW (http://mysql.he.net/) * USA [ValueClick, Los Angeles CA] WWW (http://mysql.valueclick.com/) FTP (ftp://mysql.valueclick.com/pub/mysql/Downloads/) * USA [Wisconsin University/Wisconsin] WWW (http://mirror.sit.wisc.edu/mysql/) FTP (ftp://mirror.sit.wisc.edu/mirrors/mysql/) * USA [LinuxWired/Scottsdale, AZ] WWW (http://mysql.linuxwired.net/) FTP (ftp://ftp.linuxwired.net/pub/mirrors/mysql/) * USA [adgrafix.com/Boston, MA] WWW (http://mysql.adgrafix.com/) * USA [netNumina/Cambridge, MA] WWW (http://mysql.mirrors.netnumina.com/) * USA [Ahaza Systems/Seattle, WA] WWW (http://mysql.mirrortree.com/) FTP (ftp://mysql.mirrortree.com/pub/mysql/) *South America:* * Argentina [bannerlandia.com] WWW (http://mysql.bannerlandia.com.ar/) FTP (ftp://mysql.bannerlandia.com.ar/mirrors/mysql/) * Chile [Vision] WWW (http://mysql.vision.cl/) * Chile [PSINet] WWW (http://mysql.psinet.cl/) FTP (ftp://ftp.psinet.cl/pub/database/mysql/) * Chile [Tecnoera] WWW (http://mysql.tecnoera.com/) *Asia:* * China [linuxforum.net] WWW (http://www2.linuxforum.net/mirror/mysql/) * China [HKLPG/Hong Kong] WWW (http://mysql.hklpg.org) * China [Gremlins/Hong Kong] WWW (http://mysql.gremlins.com.hk/) FTP (ftp://ftp.mirrors.gremlins.com.hk/mysql/) * Indonesia [incaf.net] WWW (http://mysql.incaf.net/) * Indonesia [web.id] WWW (http://mysql.itb.web.id/) FTP (ftp://mysql.itb.web.id/pub/MySQL/) * Japan [Soft Agency] WWW (http://www.softagency.co.jp/MySQL) * Japan [u-aizu.ac.jp/Aizu] FTP (ftp://ftp.u-aizu.ac.jp/ftp/pub/dbms/mysql/mysql.com) * South Korea [Webiiz] WWW (http://mysql.webiiz.com/) * South Korea [PanworldNet] WWW (http://mysql.holywar.net/) * Singapore [HJC] WWW (http://mysql.hjc.edu.sg) FTP (ftp://ftp.hjc.edu.sg/mysql) * Taiwan [TTN] WWW (http://mysql.ttn.net) * Taiwan [nctu.edu/HsinChu] WWW (http://mysql.nctu.edu.tw/) *Africa:* * South-Africa [Mweb] WWW (http://www.mysql.mweb.co.za/) * South Africa [The Internet Solution/Johannesburg] FTP (ftp://ftp.is.co.za/linux/mysql/) Operating Systems Supported by MySQL ------------------------------------ We use GNU Autoconf, so it is possible to port *MySQL* to all modern systems with working Posix threads and a C++ compiler. (To compile only the client code, a C++ compiler is required but not threads.) We use and develop the software ourselves primarily on Sun Solaris (Versions 2.5 - 2.7) and SuSE Linux Version 7.x. Note that for many operating systems, the native thread support works only in the latest versions. *MySQL* has been reported to compile successfully on the following operating system/thread package combinations: * AIX 4.x with native threads. *Note IBM-AIX::. * Amiga. * BSDI 2.x with the included MIT-pthreads package. *Note BSDI::. * BSDI 3.0, 3.1 and 4.x with native threads. *Note BSDI::. * DEC Unix 4.x with native threads. *Note Alpha-DEC-UNIX::. * FreeBSD 2.x with the included MIT-pthreads package. *Note FreeBSD::. * FreeBSD 3.x and 4.x with native threads. *Note FreeBSD::. * HP-UX 10.20 with the included MIT-pthreads package. *Note HP-UX 10.20::. * HP-UX 11.x with the native threads. *Note HP-UX 11.x::. * Linux 2.0+ with LinuxThreads 0.7.1+ or `glibc' 2.0.7+. *Note Linux::. * Mac OS X Server. *Note Mac OS X::. * NetBSD 1.3/1.4 Intel and NetBSD 1.3 Alpha (Requires GNU make). *Note NetBSD::. * OpenBSD > 2.5 with native therads. OpenBSD < 2.5 with the included MIT-pthreads package. *Note OpenBSD::. * OS/2 Warp 3, FixPack 29 and OS/2 Warp 4, FixPack 4. *Note OS/2::. * SGI Irix 6.x with native threads. *Note SGI-Irix::. * Solaris 2.5 and above with native threads on SPARC and x86. *Note Solaris::. * SunOS 4.x with the included MIT-pthreads package. *Note Solaris::. * SCO OpenServer with a recent port of the FSU Pthreads package. *Note SCO::. * SCO UnixWare 7.0.1. *Note SCO Unixware::. * Tru64 Unix * Win95, Win98, NT, and Win2000. *Note Windows::. Note that not all platforms are suited equally well for running *MySQL*. How well a certain platform is suited for a high-load mission critical *MySQL* server is determined by the following factors: * General stability of the thread library. A platform may have excellent reputation otherwise, but if the thread library is unstable in the code that is called by *MySQL*, even if everything else is perfect, *MySQL* will be only as stable as the thread library. * The ability of the kernel and/or thread library to take advantage of *SMP* on multi-processor systems. In other words, when a process creates a thread, it should be possible for that thread to run on a different CPU than the original process. * The ability of the kernel and/or the thread library to run many threads which acquire/release a mutex over a short critical region frequently without excessive context switches. In other words, if the implementation of `pthread_mutex_lock()' is too anxious to yield CPU, this will hurt *MySQL* tremendously. If this issue is not taken care of, adding extra CPUs will actually make *MySQL* slower. * General file system stability/performance. * Ability of the file system to deal with large files at all and deal with them efficiently, if your tables are big. * Our level of expertise here at *MySQL AB* with the platform. If we know a platform well, we introduce platform-specific optimizations/fixes enabled at compile time. We can also provide advice on configuring your system optimally for *MySQL*. * The amount of testing of similar configurations we have done internally. * The number of users that have successfully run *MySQL* on that platform in similar configurations. If this number is high, the chances of hitting some platform-specific surprise are much smaller. Based on the above criteria, the best platforms for running *MySQL* at this point are x86 with SuSE Linux 7.1, 2.4 kernel and ReiserFS (or any similar Linux distribution) and Sparc with Solaris 2.7 or 2.8. FreeBSD comes third, but we really hope it will join the top club once the thread library is improved. We also hope that at some point we will be able to include all other platforms on which *MySQL* compiles, runs ok, but not quite with the same level of stability and performance, into the top category. This will require some effort on our part in cooperation with the developers of the OS/library components *MySQL* depends upon. If you are interested in making one of those components better, are in a position to influence their development, and need more detailed instructions on what *MySQL* needs to run better, send an e-mail to . Please note that the comparison above is not to say that one OS is better or worse than the other in general. We are talking about choosing a particular OS for a dedicated purpose - running *MySQL*, and compare platforms in that regard only. With this in mind, the result of this comparison would be different if we included more issues into it. And in some cases, the reason one OS is better than the other could simply be that we have put forth more effort into testing on and optimizing for that particular platform. We are just stating our observations to help you make a decision on which platform to use *MySQL* on in your setup. Which MySQL Version to Use -------------------------- The first decision to make is whether you want to use the latest development release or the last stable release: * Normally, if you are beginning to use *MySQL* for the first time or trying to port it to some system for which there is no binary distribution, we recommend going with the stable release (currently Version 3.23.41. Note that all *MySQL* releases are checked with the *MySQL* benchmarks and an extensive test suite before each release. * Otherwise, if you are running an old system and want to upgrade, but don't want to take chances with a non-seamless upgrade, you should upgrade to the latest in the same branch you are using (where only the last version number is newer than yours). We have tried to fix only fatal bugs and make small, relatively safe changes to that version. The second decision to make is whether you want to use a source distribution or a binary distribution. In most cases you should probably use a binary distribution, if one exists for your platform, as this generally will be easier to install than a source distribution. In the following cases you probably will be better off with a source installation: * If you want to install *MySQL* at some explicit location. (The standard binary distributions are "ready to run" at any place, but you may want to get even more flexibility). * To be able to satisfy different user requirements, we are providing two different binary versions; One compiled with the non-transactional table handlers, (a small, fast binary), and one configured with the most important extended options like transaction-safe tables. Both versions are compiled from the same source distribution. All native `MySQL' clients can connect to both *MySQL* versions. The extended *MySQL* binary distribution is marked with the `-max' suffix and is configured with the same options as `mysqld-max'. *Note `mysqld-max': mysqld-max. If you want to use the `MySQL-Max' RPM, you must first install the standard `MySQL' RPM. * If you want to configure `mysqld' with some extra features that are NOT in the standard binary distributions. Here is a list of the most common extra options that you may want to use: * `--with-berkeley-db' * `--with-innodb' * `--with-raid' * `--with-libwrap' * `--with-named-z-lib (This is done for some of the binaries)' * `--with-debug[=full]' * The default binary distribution is normally compiled with support for all characters sets and should work on a variety of processors from the same processor family. If you want a faster *MySQL* server you may want to recompile it with support for only the character sets you need, use a better compiler (like `pgcc') or use compiler options that are better optimized for your processor. * If you have found a bug and reported it to the *MySQL* development team you will probably receive a patch that you need to apply to the source distribution to get the bug fixed. * If you want to read (and/or modify) the C and C++ code that makes up *MySQL*, you should get a source distribution. The source code is always the ultimate manual. Source distributions also contain more tests and examples than binary distributions. The *MySQL* naming scheme uses release numbers that consist of three numbers and a suffix. For example, a release name like `mysql-3.21.17-beta' is interpreted like this: * The first number (`3') describes the file format. All Version 3 releases have the same file format. * The second number (`21') is the release level. Normally there are two to choose from. One is the release/stable branch (currently `23') and the other is the development branch (currently `4.0'). Normally both are stable, but the development version may have quirks, missing documentation on new features, or may fail to compile on some systems. * The third number (`17') is the version number within the release level. This is incremented for each new distribution. Usually you want the latest version for the release level you have chosen. * The suffix (`beta') indicates the stability level of the release. The possible suffixes are: - `alpha' indicates that the release contains some large section of new code that hasn't been 100% tested. Known bugs (usually there are none) should be documented in the News section. *Note News::. There are also new commands and extensions in most alpha releases. Active development that may involve major code changes can occur on an alpha release, but everything will be tested before doing a release. There should be no known bugs in any *MySQL* release. - `beta' means that all new code has been tested. No major new features that could cause corruption on old code are added. There should be no known bugs. A version changes from alpha to beta when there haven't been any reported fatal bugs within an alpha version for at least a month and we don't plan to add any features that could make any old command more unreliable. - `gamma' is a beta that has been around a while and seems to work fine. Only minor fixes are added. This is what many other companies call a release. - If there is no suffix, it means that the version has been run for a while at many different sites with no reports of bugs other than platform-specific bugs. Only critical bug fixes are applied to the release. This is what we call a stable release. All versions of *MySQL* are run through our standard tests and benchmarks to ensure that they are relatively safe to use. Because the standard tests are extended over time to check for all previously found bugs, the test suite keeps getting better. Note that all releases have been tested at least with: An internal test suite This is part of a production system for a customer. It has many tables with hundreds of megabytes of data. The *MySQL* benchmark suite This runs a range of common queries. It is also a test to see whether the latest batch of optimizations actually made the code faster. *Note MySQL Benchmarks::. The `crash-me' test This tries to determine what features the database supports and what its capabilities and limitations are. *Note MySQL Benchmarks::. Another test is that we use the newest *MySQL* version in our internal production environment, on at least one machine. We have more than 100 gigabytes of data to work with. Installation Layouts -------------------- This section describes the default layout of the directories created by installing binary and source distributions. A binary distribution is installed by unpacking it at the installation location you choose (typically `/usr/local/mysql') and creates the following directories in that location: *Directory* *Contents of directory* `bin' Client programs and the `mysqld' server `data' Log files, databases `include' Include (header) files `lib' Libraries `scripts' `mysql_install_db' `share/mysql' Error message files `sql-bench' Benchmarks A source distribution is installed after you configure and compile it. By default, the installation step installs files under `/usr/local', in the following subdirectories: *Directory* *Contents of directory* `bin' Client programs and scripts `include/mysql' Include (header) files `info' Documentation in Info format `lib/mysql' Libraries `libexec' The `mysqld' server `share/mysql' Error message files `sql-bench' Benchmarks and `crash-me' test `var' Databases and log files Within an installation directory, the layout of a source installation differs from that of a binary installation in the following ways: * The `mysqld' server is installed in the `libexec' directory rather than in the `bin' directory. * The data directory is `var' rather than `data'. * `mysql_install_db' is installed in the `/usr/local/bin' directory rather than in `/usr/local/mysql/scripts'. * The header file and library directories are `include/mysql' and `lib/mysql' rather than `include' and `lib'. You can create your own binary installation from a compiled source distribution by executing the script `scripts/make_binary_distribution'. How and When Updates Are Released --------------------------------- *MySQL* is evolving quite rapidly here at *MySQL AB* and we want to share this with other *MySQL* users. We try to make a release when we have very useful features that others seem to have a need for. We also try to help out users who request features that are easy to implement. We take note of what our licensed users want to have, and we especially take note of what our extended e-mail supported customers want and try to help them out. No one has to download a new release. The News section will tell you if the new release has something you really want. *Note News::. We use the following policy when updating *MySQL*: * For each minor update, the last number in the version string is incremented. When there are major new features or minor incompatibilities with previous versions, the second number in the version string is incremented. When the file format changes, the first number is increased. * Stable tested releases are meant to appear about 1-2 times a year, but if small bugs are found, a release with only bug fixes will be released. * Working releases are meant to appear about every 1-8 weeks. * Binary distributions for some platforms will be made by us for major releases. Other people may make binary distributions for other systems but probably less frequently. * We usually make patches available as soon as we have located and fixed small bugs. * For non-critical but annoying bugs, we will make patches available if they are sent to us. Otherwise we will combine many of them into a larger patch. * If there is, by any chance, a fatal bug in a release we will make a new release as soon as possible. We would like other companies to do this, too. The current stable release is Version 3.23; We have already moved active development to Version 4.0. Bugs will still be fixed in the stable version. We don't believe in a complete freeze, as this also leaves out bug fixes and things that "must be done." "Somewhat frozen" means that we may add small things that "almost surely will not affect anything that's already working." MySQL Binaries Compiled by MySQL AB ----------------------------------- As a service, we at *MySQL AB* provide a set of binary distributions of *MySQL* that are compiled at our site or at sites where customers kindly have given us access to their machines. These distributions are generated with `scripts/make_binary_distribution' and are configured with the following compilers and options: SunOS 4.1.4 2 sun4c with `gcc' 2.7.2.1 `CC=gcc CXX=gcc CXXFLAGS="-O3 -felide-constructors" ./configure --prefix=/usr/local/mysql --disable-shared --with-extra-charsets=complex --enable-assembler' SunOS 5.5.1 (and above) sun4u with `egcs' 1.0.3a or 2.90.27 or gcc 2.95.2 and newer `CC=gcc CFLAGS="-O3" CXX=gcc CXXFLAGS="-O3 -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --with-low-memory --with-extra-charsets=complex --enable-assembler' SunOS 5.6 i86pc with `gcc' 2.8.1 `CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-low-memory --with-extra-charsets=complex' Linux 2.0.33 i386 with `pgcc' 2.90.29 (`egcs' 1.0.3a) `CFLAGS="-O3 -mpentium -mstack-align-double" CXX=gcc CXXFLAGS="-O3 -mpentium -mstack-align-double -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static --with-extra-charsets=complex' Linux 2.2.x with x686 with `gcc' 2.95.2 `CFLAGS="-O3 -mpentiumpro" CXX=gcc CXXFLAGS="-O3 -mpentiumpro -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static --disable-shared --with-extra-charset=complex' SCO 3.2v5.0.4 i386 with `gcc' 2.7-95q4 `CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-extra-charsets=complex' AIX 2 4 with `gcc' 2.7.2.2 `CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-extra-charsets=complex' OSF1 V4.0 564 alpha with `gcc' 2.8.1 `CC=gcc CFLAGS=-O CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-low-memory --with-extra-charsets=complex' Irix 6.3 IP32 with `gcc' 2.8.0 `CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-extra-charsets=complex' BSDI BSD/OS 3.1 i386 with `gcc' 2.7.2.1 `CC=gcc CXX=gcc CXXFLAGS=-O ./configure --prefix=/usr/local/mysql --with-extra-charsets=complex' BSDI BSD/OS 2.1 i386 with `gcc' 2.7.2 `CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-extra-charsets=complex' Anyone who has more optimal options for any of the configurations listed above can always mail them to the developer's mailing list at . RPM distributions prior to *MySQL* Version 3.22 are user-contributed. Beginning with Version 3.22, the RPMs are generated by us at *MySQL AB*. If you want to compile a debug version of *MySQL*, you should add `--with-debug' or `--with-debug=full' to the above configure lines and remove any `-fomit-frame-pointer' options. Installing a MySQL Source Distribution ====================================== Before you proceed with the source installation, check first to see if our binary is available for your platform and if it will work for you. We put in a lot of effort into making sure that our binaries are built with the best possible options. You need the following tools to build and install *MySQL* from source: * GNU `gunzip' to uncompress the distribution. * A reasonable `tar' to unpack the distribution. GNU `tar' is known to work. Sun `tar' is known to have problems. * A working ANSI C++ compiler. `gcc' >= 2.95.2, `egcs' >= 1.0.2 or `egcs 2.91.66', SGI C++, and SunPro C++ are some of the compilers that are known to work. `libg++' is not needed when using `gcc'. `gcc' 2.7.x has a bug that makes it impossible to compile some perfectly legal C++ files, such as `sql/sql_base.cc'. If you only have `gcc' 2.7.x, you must upgrade your `gcc' to be able to compile *MySQL*. `gcc' 2.8.1 is also known to have problems on some platforms so it should be avoided if there exists a new compiler for the platform.. `gcc' >= 2.95.2 is recommended when compiling *MySQL* Version 3.23.x. * A good `make' program. GNU `make' is always recommended and is sometimes required. If you have problems, we recommend trying GNU `make' 3.75 or newer. If you are using a recent version of *gcc*, recent enough to understand `-fno-exceptions' option, it is *VERY IMPORTANT* that you use it. Otherwise, you may compile a binary that crashes randomly. We also recommend that you use `-felide-contructors' and `-fno-rtti' along with `-fno-exceptions'. When in doubt, do the following: CFLAGS="-O3" CXX=gcc CXXFLAGS="-O3 -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static On most systems this will give you a fast and stable binary. If you run into problems, *PLEASE ALWAYS USE `mysqlbug'* when posting questions to . Even if the problem isn't a bug, `mysqlbug' gathers system information that will help others solve your problem. By not using `mysqlbug', you lessen the likelihood of getting a solution to your problem! You will find `mysqlbug' in the `scripts' directory after you unpack the distribution. *Note Bug reports::. Quick Installation Overview --------------------------- The basic commands you must execute to install a *MySQL* source distribution are: shell> groupadd mysql shell> useradd -g mysql mysql shell> gunzip < mysql-VERSION.tar.gz | tar -xvf - shell> cd mysql-VERSION shell> ./configure --prefix=/usr/local/mysql shell> make shell> make install shell> scripts/mysql_install_db shell> chown -R root /usr/local/mysql shell> chown -R mysql /usr/local/mysql/var shell> chgrp -R mysql /usr/local/mysql shell> cp support-files/my-medium.cnf /etc/my.cnf shell> /usr/local/mysql/bin/safe_mysqld --user=mysql & If you want have support for InnoDB tables, you should edit the `/etc/my.cnf' file and remove the `#' character before the parameters that starts with `innodb_...'. *Note Option files::. *Note InnoDB start::. If you start from a source RPM, then do the following: shell> rpm --rebuild MySQL-VERSION.src.rpm This will make a binary RPM that you can install. You can add new users using the `bin/mysql_setpermission' script if you install the `DBI' and `Msql-Mysql-modules' Perl modules. A more detailed description follows. To install a source distribution, follow the steps below, then proceed to *Note Post-installation::, for post-installation initialization and testing: 1. Pick the directory under which you want to unpack the distribution, and move into it. 2. Obtain a distribution file from one of the sites listed in *Note Getting *MySQL*: Getting MySQL. 3. If you are interested in using Berkeley DB tables with MySQL, you will need to obtain a patched version of the Berkeley DB source code. Please read the chapter on Berkeley DB tables before proceeding. *Note BDB::. *MySQL* source distributions are provided as compressed `tar' archives and have names like `mysql-VERSION.tar.gz', where `VERSION' is a number like 3.23.41. 4. Add a user and group for `mysqld' to run as: shell> groupadd mysql shell> useradd -g mysql mysql These commands add the `mysql' group, and the `mysql' user. The syntax for `useradd' and `groupadd' may differ slightly on different versions of Unix. They may also be called `adduser' and `addgroup'. You may wish to call the user and group something else instead of `mysql'. 5. Unpack the distribution into the current directory: shell> gunzip < /path/to/mysql-VERSION.tar.gz | tar xvf - This command creates a directory named `mysql-VERSION'. 6. Change into the top-level directory of the unpacked distribution: shell> cd mysql-VERSION Note that currently you must configure and build *MySQL* from this top-level directory. You can not build it in a different directory. 7. Configure the release and compile everything: shell> ./configure --prefix=/usr/local/mysql shell> make When you run `configure', you might want to specify some options. Run `./configure --help' for a list of options. *Note `configure' options: configure options, discusses some of the more useful options. If `configure' fails, and you are going to send mail to to ask for assistance, please include any lines from `config.log' that you think can help solve the problem. Also include the last couple of lines of output from `configure' if `configure' aborts. Post the bug report using the `mysqlbug' script. *Note Bug reports::. If the compile fails, see *Note Compilation problems::, for help with a number of common problems. 8. Install everything: shell> make install You might need to run this command as `root'. 9. Create the *MySQL* grant tables (necessary only if you haven't installed *MySQL* before): shell> scripts/mysql_install_db Note that *MySQL* versions older than Version 3.22.10 started the *MySQL* server when you run `mysql_install_db'. This is no longer true! 10. Change ownership of binaries to `root' and ownership of the data directory to the user that you will run `mysqld' as: shell> chown -R root /usr/local/mysql shell> chown -R mysql /usr/local/mysql/var shell> chgrp -R mysql /usr/local/mysql The first command changes the `owner' attribute of the files to the `root' user, the second one changes the `owner' attribute of the data directory to the `mysql' user, and the third one changes the `group' attribute to the `mysql' group. 11. If you want to install support for the Perl `DBI'/`DBD' interface, see *Note Perl support::. 12. If you would like *MySQL* to start automatically when you boot your machine, you can copy `support-files/mysql.server' to the location where your system has its startup files. More information can be found in the `support-files/mysql.server' script itself and in *Note Automatic start::. After everything has been installed, you should initialize and test your distribution: shell> /usr/local/mysql/bin/safe_mysqld --user=mysql & If that command fails immediately with `mysqld daemon ended' then you can find some information in the file `mysql-data-directory/'hostname'.err'. The likely reason is that you already have another `mysqld' server running. *Note Multiple servers::. *Note Post-installation::. Applying Patches ---------------- Sometimes patches appear on the mailing list or are placed in the patches area (http://www.mysql.com/Downloads/Patches) of the *MySQL* Web site. To apply a patch from the mailing list, save the message in which the patch appears in a file, change into the top-level directory of your *MySQL* source tree, and run these commands: shell> patch -p1 < patch-file-name shell> rm config.cache shell> make clean Patches from the FTP site are distributed as plain text files or as files compressed with `gzip'. Apply a plain patch as shown above for mailing list patches. To apply a compressed patch, change into the top-level directory of your *MySQL* source tree and run these commands: shell> gunzip < patch-file-name.gz | patch -p1 shell> rm config.cache shell> make clean After applying a patch, follow the instructions for a normal source install, beginning with the `./configure' step. After running the `make install' step, restart your *MySQL* server. You may need to bring down any currently running server before you run `make install'. (Use `mysqladmin shutdown' to do this.) Some systems do not allow you to install a new version of a program if it replaces the version that is currently executing. Typical `configure' Options --------------------------- The `configure' script gives you a great deal of control over how you configure your *MySQL* distribution. Typically you do this using options on the `configure' command line. You can also affect `configure' using certain environment variables. *Note Environment variables::. For a list of options supported by `configure', run this command: shell> ./configure --help Some of the more commonly-used `configure' options are described below: * To compile just the *MySQL* client libraries and client programs and not the server, use the `--without-server' option: shell> ./configure --without-server If you don't have a C++ compiler, `mysql' will not compile (it is the one client program that requires C++). In this case, you can remove the code in `configure' that tests for the C++ compiler and then run `./configure' with the `--without-server' option. The compile step will still try to build `mysql', but you can ignore any warnings about `mysql.cc'. (If `make' stops, try `make -k' to tell it to continue with the rest of the build even if errors occur.) * If you don't want your log files and database directories located under `/usr/local/var', use a `configure' command, something like one of these: shell> ./configure --prefix=/usr/local/mysql shell> ./configure --prefix=/usr/local \ --localstatedir=/usr/local/mysql/data The first command changes the installation prefix so that everything is installed under `/usr/local/mysql' rather than the default of `/usr/local'. The second command preserves the default installation prefix, but overrides the default location for database directories (normally `/usr/local/var') and changes it to `/usr/local/mysql/data'. * If you are using Unix and you want the *MySQL* socket located somewhere other than the default location (normally in the directory `/tmp' or `/var/run') use a `configure' command like this: shell> ./configure --with-unix-socket-path=/usr/local/mysql/tmp/mysql.sock Note that the given file must be an absolute pathname! * If you want to compile statically linked programs (for example, to make a binary distribution, to get more speed, or to work around problems with some RedHat Linux distributions), run `configure' like this: shell> ./configure --with-client-ldflags=-all-static \ --with-mysqld-ldflags=-all-static * If you are using `gcc' and don't have `libg++' or `libstdc++' installed, you can tell `configure' to use `gcc' as your C++ compiler: shell> CC=gcc CXX=gcc ./configure When you use `gcc' as your C++ compiler, it will not attempt to link in `libg++' or `libstdc++'. Here is some common environment variables to set depending on the compiler you are using: gcc 2.7.2.1 CC=gcc CXX=gcc CXXFLAGS="-O3 -felide-constructors" egcs 1.0.3a CC=gcc CXX=gcc CXXFLAGS="-O3 -felide-constructors -fno-exceptions -fno-rtti" gcc 2.95.2 CFLAGS="-O3 -mpentiumpro" CXX=gcc CXXFLAGS="-O3 -mpentiumpro -felide-constructors -fno-exceptions -fno-rtti" pgcc 2.90.29 CFLAGS="-O3 -mpentiumpro -mstack-align-double" or newer CXX=gcc CXXFLAGS="-O3 -mpentiumpro -mstack-align-double -felide-constructors -fno-exceptions -fno-rtti" In most cases you can get a reasonably optimal *MySQL* binary by using the options from the above and adding the following options to the configure line: --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static The full configure line would in other words be something like the following for all recent gcc versions: CFLAGS="-O3 -mpentiumpro" CXX=gcc CXXFLAGS="-O3 -mpentiumpro -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static The binaries we provide on the *MySQL* Web site at `http://www.mysql.com' are all compiled with full optimization and should be perfect for most users. *Note MySQL binaries::. There are some things you can tweak to make an even faster binary, but this is only for advanced users. *Note Compile and link options::. If the build fails and produces errors about your compiler or linker not being able to create the shared library `libmysqlclient.so.#' (`#' is a version number), you can work around this problem by giving the `--disable-shared' option to `configure'. In this case, `configure' will not build a shared `libmysqlclient.so.#' library. * You can configure *MySQL* not to use `DEFAULT' column values for non-`NULL' columns (that is, columns that are not allowed to be `NULL'). This causes `INSERT' statements to generate an error unless you explicitly specify values for all columns that require a non-`NULL' value. To suppress use of default values, run `configure' like this: shell> CXXFLAGS=-DDONT_USE_DEFAULT_FIELDS ./configure * By default, *MySQL* uses the ISO-8859-1 (Latin1) character set. To change the default set, use the `--with-charset' option: shell> ./configure --with-charset=CHARSET `CHARSET' may be one of `big5', `cp1251', `cp1257', `czech', `danish', `dec8', `dos', `euc_kr', `gb2312', `gbk', `german1', `hebrew', `hp8', `hungarian', `koi8_ru', `koi8_ukr', `latin1', `latin2', `sjis', `swe7', `tis620', `ujis', `usa7', or `win1251ukr'. *Note Character sets::. If you want to convert characters between the server and the client, you should take a look at the `SET OPTION CHARACTER SET' command. *Note `SET OPTION': SET OPTION. *Warning:* If you change character sets after having created any tables, you will have to run `myisamchk -r -q' on every table. Your indexes may be sorted incorrectly otherwise. (This can happen if you install *MySQL*, create some tables, then reconfigure *MySQL* to use a different character set and reinstall it.) With the option `--with-extra-charset=LIST' you can define which additional character sets should be incompiled in the server. Here `LIST' is either a list of character set separated with space, `complex' to include all characters that can't be dynamically loaded or `all' to include all character sets into the binaries. * To configure *MySQL* with debugging code, use the `--with-debug' option: shell> ./configure --with-debug This causes a safe memory allocator to be included that can find some errors and that provides output about what is happening. *Note Debugging server::. * If your client programs are using threads, you need to also compile a thread-safe version of the *MySQL* client library with the `--with-thread-safe-client' configure options. This will create a `libmysqlclient_r' library with which you should link your threaded applications. *Note Thread-safe clients::. * Options that pertain to particular systems can be found in the system-specific section of this manual. *Note Operating System Specific Notes::. Installing from the Development Source Tree ------------------------------------------- *CAUTION:* You should read this section only if you are interested in helping us test our new code. If you just want to get *MySQL* up and running on your system, you should use a standard release distribution (either a source or binary distribution will do). To obtain our most recent development source tree, use these instructions: 1. Download *BitKeeper* from `http://www.bitmover.com/cgi-bin/download.cgi'. You will need *Bitkeeper* 2.0 or newer to access our repository. 2. Follow the instructions to install it. 3. After *BitKeeper* is installed, use this command if you want to clone the *MySQL* 3.23 branch: shell> bk clone bk://work.mysql.com:7000 mysql To clone the 4.0 branch, use this command instead: shell> bk clone bk://work.mysql.com:7001 mysql-4.0 The initial download of the source tree may take a while, depending on the speed of your connection; be patient. 4. You will need GNU `autoconf', `automake', `libtool', and `m4' to run the next set of commands. If you get some strange error during this stage, check that you really have `libtool' installed! shell> cd mysql shell> bk -r edit shell> aclocal; autoheader; autoconf; automake; shell> ./configure # Add your favorite options here shell> make A collection of our standard configure scripts is located in the `BUILD/' subdirectory. If you are lazy, you can use `BUILD/compile-pentium-debug'. To compile on a different architecture, modify the script removing flags that are Pentium-specific. 5. When the build is done, run `make install'. Be careful with this on a production machine; the command may overwrite your live release installation. If you have another installation of *MySQL*, we recommand that you run `./configure' with different values for the `prefix', `tcp-port', and `unix-socket-path' options than those used for your production server. 6. Play hard with your new installation and try to make the new features crash. Start by running `make test'. *Note MySQL test suite::. 7. If you have gotten to the `make' stage and the distribution does not compile, please report it to . If you have installed the latest versions of the required GNU tools, and they crash trying to process our configuration files, please report that also. However, if you execute `aclocal' and get a `command not found' error or a similar problem, do not report it. Instead, make sure all the necessary tools are installed and that your `PATH' variable is set correctly so your shell can find them. 8. After the initial `bk clone' operation to get the source tree, you should run `bk pull' periodically to get the updates. 9. You can examine the change history for the tree with all the diffs by using `bk sccstool'. If you see some funny diffs or code that you have a question about, do not hesitate to send e-mail to . Also, if you think you have a better idea on how to do something, send an email to the same address with a patch. `bk diffs' will produce a patch for you after you have made changes to the source. If you do not have the time to code your idea, just send a description. 10. *BitKeeper* has a nice help utility that you can access via `bk helptool'. Problems Compiling? ------------------- All *MySQL* programs compile cleanly for us with no warnings on Solaris using `gcc'. On other systems, warnings may occur due to differences in system include files. See *Note MIT-pthreads:: for warnings that may occur when using MIT-pthreads. For other problems, check the list below. The solution to many problems involves reconfiguring. If you do need to reconfigure, take note of the following: * If `configure' is run after it already has been run, it may use information that was gathered during its previous invocation. This information is stored in `config.cache'. When `configure' starts up, it looks for that file and reads its contents if it exists, on the assumption that the information is still correct. That assumption is invalid when you reconfigure. * Each time you run `configure', you must run `make' again to recompile. However, you may want to remove old object files from previous builds first, because they were compiled using different configuration options. To prevent old configuration information or object files from being used, run these commands before rerunning `configure': shell> rm config.cache shell> make clean Alternatively, you can run `make distclean'. The list below describes some of the problems compiling *MySQL* that have been found to occur most often: * If you get errors when compiling `sql_yacc.cc', such as the ones shown below, you have probably run out of memory or swap space: Internal compiler error: program cc1plus got fatal signal 11 or Out of virtual memory or Virtual memory exhausted The problem is that `gcc' requires huge amounts of memory to compile `sql_yacc.cc' with inline functions. Try running `configure' with the `--with-low-memory' option: shell> ./configure --with-low-memory This option causes `-fno-inline' to be added to the compile line if you are using `gcc' and `-O0' if you are using something else. You should try the `--with-low-memory' option even if you have so much memory and swap space that you think you can't possibly have run out. This problem has been observed to occur even on systems with generous hardware configurations, and the `--with-low-memory' option usually fixes it. * By default, `configure' picks `c++' as the compiler name and GNU `c++' links with `-lg++'. If you are using `gcc', that behavior can cause problems during configuration such as this: configure: error: installation or configuration problem: C++ compiler cannot create executables. You might also observe problems during compilation related to `g++', `libg++', or `libstdc++'. One cause of these problems is that you may not have `g++', or you may have `g++' but not `libg++', or `libstdc++'. Take a look at the `config.log' file. It should contain the exact reason why your c++ compiler didn't work! To work around these problems, you can use `gcc' as your C++ compiler. Try setting the environment variable `CXX' to `"gcc -O3"'. For example: shell> CXX="gcc -O3" ./configure This works because `gcc' compiles C++ sources as well as `g++' does, but does not link in `libg++' or `libstdc++' by default. Another way to fix these problems, of course, is to install `g++', `libg++' and `libstdc++'. * If your compile fails with errors, such as any of the following, you must upgrade your version of `make' to GNU `make': making all in mit-pthreads make: Fatal error in reader: Makefile, line 18: Badly formed macro assignment or make: file `Makefile' line 18: Must be a separator (: or pthread.h: No such file or directory Solaris and FreeBSD are known to have troublesome `make' programs. GNU `make' Version 3.75 is known to work. * If you want to define flags to be used by your C or C++ compilers, do so by adding the flags to the `CFLAGS' and `CXXFLAGS' environment variables. You can also specify the compiler names this way using `CC' and `CXX'. For example: shell> CC=gcc shell> CFLAGS=-O3 shell> CXX=gcc shell> CXXFLAGS=-O3 shell> export CC CFLAGS CXX CXXFLAGS See *Note MySQL binaries::, for a list of flag definitions that have been found to be useful on various systems. * If you get an error message like this, you need to upgrade your `gcc' compiler: client/libmysql.c:273: parse error before `__attribute__' `gcc' 2.8.1 is known to work, but we recommend using `gcc' 2.95.2 or `egcs' 1.0.3a instead. * If you get errors such as those shown below when compiling `mysqld', `configure' didn't correctly detect the type of the last argument to `accept()', `getsockname()', or `getpeername()': cxx: Error: mysqld.cc, line 645: In this statement, the referenced type of the pointer value "&length" is "unsigned long", which is not compatible with "int". new_sock = accept(sock, (struct sockaddr *)&cAddr, &length); To fix this, edit the `config.h' file (which is generated by `configure'). Look for these lines: /* Define as the base type of the last arg to accept */ #define SOCKET_SIZE_TYPE XXX Change `XXX' to `size_t' or `int', depending on your operating system. (Note that you will have to do this each time you run `configure', because `configure' regenerates `config.h'.) * The `sql_yacc.cc' file is generated from `sql_yacc.yy'. Normally the build process doesn't need to create `sql_yacc.cc', because *MySQL* comes with an already-generated copy. However, if you do need to re-create it, you might encounter this error: "sql_yacc.yy", line xxx fatal: default action causes potential... This is a sign that your version of `yacc' is deficient. You probably need to install `bison' (the GNU version of `yacc') and use that instead. * If you need to debug `mysqld' or a *MySQL* client, run `configure' with the `--with-debug' option, then recompile and link your clients with the new client library. *Note Debugging client::. MIT-pthreads Notes ------------------ This section describes some of the issues involved in using MIT-pthreads. Note that on Linux you should NOT use MIT-pthreads but install LinuxThreads! *Note Linux::. If your system does not provide native thread support, you will need to build *MySQL* using the MIT-pthreads package. This includes older FreeBSD systems, SunOS 4.x, Solaris 2.4 and earlier, and some others. *Note Which OS::. * On most systems, you can force MIT-pthreads to be used by running `configure' with the `--with-mit-threads' option: shell> ./configure --with-mit-threads Building in a non-source directory is not supported when using MIT-pthreads, because we want to minimize our changes to this code. * The checks that determine whether or not to use MIT-pthreads occur only during the part of the configuration process that deals with the server code. If you have configured the distribution using `--without-server' to build only the client code, clients will not know whether or not MIT-pthreads is being used and will use Unix socket connections by default. Because Unix sockets do not work under MIT-pthreads, this means you will need to use `-h' or `--host' when you run client programs. * When *MySQL* is compiled using MIT-pthreads, system locking is disabled by default for performance reasons. You can tell the server to use system locking with the `--use-locking' option. * Sometimes the pthread `bind()' command fails to bind to a socket without any error message (at least on Solaris). The result is that all connections to the server fail. For example: shell> mysqladmin version mysqladmin: connect to server at '' failed; error: 'Can't connect to mysql server on localhost (146)' The solution to this is to kill the `mysqld' server and restart it. This has only happened to us when we have forced the server down and done a restart immediately. * With MIT-pthreads, the `sleep()' system call isn't interruptible with `SIGINT' (break). This is only noticeable when you run `mysqladmin --sleep'. You must wait for the `sleep()' call to terminate before the interrupt is served and the process stops. * When linking, you may receive warning messages like these (at least on Solaris); they can be ignored: ld: warning: symbol `_iob' has differing sizes: (file /my/local/pthreads/lib/libpthread.a(findfp.o) value=0x4; file /usr/lib/libc.so value=0x140); /my/local/pthreads/lib/libpthread.a(findfp.o) definition taken ld: warning: symbol `__iob' has differing sizes: (file /my/local/pthreads/lib/libpthread.a(findfp.o) value=0x4; file /usr/lib/libc.so value=0x140); /my/local/pthreads/lib/libpthread.a(findfp.o) definition taken * Some other warnings also can be ignored: implicit declaration of function `int strtoll(...)' implicit declaration of function `int strtoul(...)' * We haven't gotten `readline' to work with MIT-pthreads. (This isn't needed, but may be interesting for someone.) Post-installation Setup and Testing =================================== Once you've installed *MySQL* (from either a binary or source distribution), you need to initialize the grant tables, start the server, and make sure that the server works okay. You may also wish to arrange for the server to be started and stopped automatically when your system starts up and shuts down. Normally you install the grant tables and start the server like this for installation from a source distribution: shell> ./scripts/mysql_install_db shell> cd mysql_installation_directory shell> ./bin/safe_mysqld --user=mysql & For a binary distribution (not RPM or pkg packages), do this: shell> cd mysql_installation_directory shell> ./bin/mysql_install_db shell> ./bin/safe_mysqld --user=mysql & This creates the `mysql' database which will hold all database privileges, the `test' database which you can use to test *MySQL* and also privilege entries for the user that run `mysql_install_db' and a `root' user (without any passwords). This also starts the `mysqld' server. `mysql_install_db' will not overwrite any old privilege tables, so it should be safe to run in any circumstances. If you don't want to have the `test' database you can remove it with `mysqladmin -u root drop test'. Testing is most easily done from the top-level directory of the *MySQL* distribution. For a binary distribution, this is your installation directory (typically something like `/usr/local/mysql'). For a source distribution, this is the main directory of your *MySQL* source tree. In the commands shown below in this section and in the following subsections, `BINDIR' is the path to the location in which programs like `mysqladmin' and `safe_mysqld' are installed. For a binary distribution, this is the `bin' directory within the distribution. For a source distribution, `BINDIR' is probably `/usr/local/bin', unless you specified an installation directory other than `/usr/local' when you ran `configure'. `EXECDIR' is the location in which the `mysqld' server is installed. For a binary distribution, this is the same as `BINDIR'. For a source distribution, `EXECDIR' is probably `/usr/local/libexec'. Testing is described in detail below: 1. If necessary, start the `mysqld' server and set up the initial *MySQL* grant tables containing the privileges that determine how users are allowed to connect to the server. This is normally done with the `mysql_install_db' script: shell> scripts/mysql_install_db Typically, `mysql_install_db' needs to be run only the first time you install *MySQL*. Therefore, if you are upgrading an existing installation, you can skip this step. (However, `mysql_install_db' is quite safe to use and will not update any tables that already exist, so if you are unsure of what to do, you can always run `mysql_install_db'.) `mysql_install_db' creates six tables (`user', `db', `host', `tables_priv', `columns_priv', and `func') in the `mysql' database. A description of the initial privileges is given in *Note Default privileges::. Briefly, these privileges allow the *MySQL* `root' user to do anything, and allow anybody to create or use databases with a name of `'test'' or starting with `'test_''. If you don't set up the grant tables, the following error will appear in the log file when you start the server: mysqld: Can't find file: 'host.frm' The above may also happen with a binary *MySQL* distribution if you don't start *MySQL* by executing exactly `./bin/safe_mysqld'! *Note `safe_mysqld': safe_mysqld. You might need to run `mysql_install_db' as `root'. However, if you prefer, you can run the *MySQL* server as an unprivileged (non-`root') user, provided that user can read and write files in the database directory. Instructions for running *MySQL* as an unprivileged user are given in *Note Changing *MySQL* user: Changing MySQL user. If you have problems with `mysql_install_db', see *Note `mysql_install_db': mysql_install_db. There are some alternatives to running the `mysql_install_db' script as it is provided in the *MySQL* distribution: * You may want to edit `mysql_install_db' before running it, to change the initial privileges that are installed into the grant tables. This is useful if you want to install *MySQL* on a lot of machines with the same privileges. In this case you probably should need only to add a few extra `INSERT' statements to the `mysql.user' and `mysql.db' tables! * If you want to change things in the grant tables after installing them, you can run `mysql_install_db', then use `mysql -u root mysql' to connect to the grant tables as the *MySQL* `root' user and issue SQL statements to modify the grant tables directly. * It is possible to re-create the grant tables completely after they have already been created. You might want to do this if you've already installed the tables but then want to re-create them after editing `mysql_install_db'. For more information about these alternatives, see *Note Default privileges::. 2. Start the *MySQL* server like this: shell> cd mysql_installation_directory shell> bin/safe_mysqld & If you have problems starting the server, see *Note Starting server::. 3. Use `mysqladmin' to verify that the server is running. The following commands provide a simple test to check that the server is up and responding to connections: shell> BINDIR/mysqladmin version shell> BINDIR/mysqladmin variables The output from `mysqladmin version' varies slightly depending on your platform and version of *MySQL*, but should be similar to that shown below: shell> BINDIR/mysqladmin version mysqladmin Ver 8.14 Distrib 3.23.32, for linux on i586 Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB This software comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to modify and redistribute it under the GPL license Server version 3.23.32-debug Protocol version 10 Connection Localhost via Unix socket TCP port 3306 UNIX socket /tmp/mysql.sock Uptime: 16 sec Threads: 1 Questions: 9 Slow queries: 0 Opens: 7 Flush tables: 2 Open tables: 0 Queries per second avg: 0.000 Memory in use: 132K Max memory used: 16773K To get a feeling for what else you can do with `BINDIR/mysqladmin', invoke it with the `--help' option. 4. Verify that you can shut down the server: shell> BINDIR/mysqladmin -u root shutdown 5. Verify that you can restart the server. Do this using `safe_mysqld' or by invoking `mysqld' directly. For example: shell> BINDIR/safe_mysqld --log & If `safe_mysqld' fails, try running it from the *MySQL* installation directory (if you are not already there). If that doesn't work, see *Note Starting server::. 6. Run some simple tests to verify that the server is working. The output should be similar to what is shown below: shell> BINDIR/mysqlshow +-----------+ | Databases | +-----------+ | mysql | +-----------+ shell> BINDIR/mysqlshow mysql Database: mysql +--------------+ | Tables | +--------------+ | columns_priv | | db | | func | | host | | tables_priv | | user | +--------------+ shell> BINDIR/mysql -e "select host,db,user from db" mysql +------+--------+------+ | host | db | user | +------+--------+------+ | % | test | | | % | test_% | | +------+--------+------+ There is also a benchmark suite in the `sql-bench' directory (under the *MySQL* installation directory) that you can use to compare how *MySQL* performs on different platforms. The `sql-bench/Results' directory contains the results from many runs against different databases and platforms. To run all tests, execute these commands: shell> cd sql-bench shell> run-all-tests If you don't have the `sql-bench' directory, you are probably using an RPM for a binary distribution. (Source distribution RPMs include the benchmark directory.) In this case, you must first install the benchmark suite before you can use it. Beginning with *MySQL* Version 3.22, there are benchmark RPM files named `mysql-bench-VERSION-i386.rpm' that contain benchmark code and data. If you have a source distribution, you can also run the tests in the `tests' subdirectory. For example, to run `auto_increment.tst', do this: shell> BINDIR/mysql -vvf test < ./tests/auto_increment.tst The expected results are shown in the `./tests/auto_increment.res' file. Problems Running `mysql_install_db' ----------------------------------- The purpose of the `mysql_install_db' script is to generate new *MySQL* privilege tables. It will not affect any other data! It will also not do anything if you already have *MySQL* privilege tables installed! If you want to re-create your privilege tables, you should take down the `mysqld' server, if it's running, and then do something like: mv mysql-data-directory/mysql mysql-data-directory/mysql-old mysql_install_db This section lists problems you might encounter when you run `mysql_install_db': *`mysql_install_db' doesn't install the grant tables* You may find that `mysql_install_db' fails to install the grant tables and terminates after displaying the following messages: starting mysqld daemon with databases from XXXXXX mysql daemon ended In this case, you should examine the log file very carefully! The log should be located in the directory `XXXXXX' named by the error message, and should indicate why `mysqld' didn't start. If you don't understand what happened, include the log when you post a bug report using `mysqlbug'! *Note Bug reports::. *There is already a `mysqld' daemon running* In this case, you probably don't have to run `mysql_install_db' at all. You have to run `mysql_install_db' only once, when you install *MySQL* the first time. *Installing a second `mysqld' daemon doesn't work when one daemon is running* This can happen when you already have an existing *MySQL* installation, but want to put a new installation in a different place (for example, for testing, or perhaps you simply want to run two installations at the same time). Generally the problem that occurs when you try to run the second server is that it tries to use the same socket and port as the old one. In this case you will get the error message: `Can't start server: Bind on TCP/IP port: Address already in use' or `Can't start server : Bind on unix socket...'. *Note Installing many servers::. *You don't have write access to `/tmp'* If you don't have write access to create a socket file at the default place (in `/tmp') or permission to create temporary files in `/tmp,' you will get an error when running `mysql_install_db' or when starting or using `mysqld'. You can specify a different socket and temporary directory as follows: shell> TMPDIR=/some_tmp_dir/ shell> MYSQL_UNIX_PORT=/some_tmp_dir/mysqld.sock shell> export TMPDIR MYSQL_UNIX_PORT `some_tmp_dir' should be the path to some directory for which you have write permission. *Note Environment variables::. After this you should be able to run `mysql_install_db' and start the server with these commands: shell> scripts/mysql_install_db shell> BINDIR/safe_mysqld & *`mysqld' crashes immediately* If you are running RedHat Version 5.0 with a version of `glibc' older than 2.0.7-5, you should make sure you have installed all `glibc' patches! There is a lot of information about this in the *MySQL* mail archives. Links to the mail archives are available online at `http://www.mysql.com/documentation/'. Also, see *Note Linux::. You can also start `mysqld' manually using the `--skip-grant-tables' option and add the privilege information yourself using `mysql': shell> BINDIR/safe_mysqld --skip-grant-tables & shell> BINDIR/mysql -u root mysql From `mysql', manually execute the SQL commands in `mysql_install_db'. Make sure you run `mysqladmin flush-privileges' or `mysqladmin reload' afterward to tell the server to reload the grant tables. Problems Starting the MySQL Server ---------------------------------- If you are going to use tables that support transactions (BDB, InnoDB), you should first create a my.cnf file and set startup options for the table types you plan to use. *Note Table types::. Generally, you start the `mysqld' server in one of three ways: * By invoking `mysql.server'. This script is used primarily at system startup and shutdown, and is described more fully in *Note Automatic start::. * By invoking `safe_mysqld', which tries to determine the proper options for `mysqld' and then runs it with those options. *Note `safe_mysqld': safe_mysqld. * On NT you should install `mysqld' as a service as follows: bin\mysqld-nt --install # Install MySQL as a service You can now start/stop `mysqld' as follows: NET START mysql NET STOP mysql Note that in this case you can't use any other options for `mysqld'! You can remove the service as follows: bin\mysqld-nt --remove # remove MySQL as a service * By invoking `mysqld' directly. When the `mysqld' daemon starts up, it changes directory to the data directory. This is where it expects to write log files and the pid (process ID) file, and where it expects to find databases. The data directory location is hardwired in when the distribution is compiled. However, if `mysqld' expects to find the data directory somewhere other than where it really is on your system, it will not work properly. If you have problems with incorrect paths, you can find out what options `mysqld' allows and what the default path settings are by invoking `mysqld' with the `--help' option. You can override the defaults by specifying the correct pathnames as command-line arguments to `mysqld'. (These options can be used with `safe_mysqld' as well.) Normally you should need to tell `mysqld' only the base directory under which *MySQL* is installed. You can do this with the `--basedir' option. You can also use `--help' to check the effect of changing path options (note that `--help' _must_ be the final option of the `mysqld' command). For example: shell> EXECDIR/mysqld --basedir=/usr/local --help Once you determine the path settings you want, start the server without the `--help' option. Whichever method you use to start the server, if it fails to start up correctly, check the log file to see if you can find out why. Log files are located in the data directory (typically `/usr/local/mysql/data' for a binary distribution, `/usr/local/var' for a source distribution, `\mysql\data\mysql.err' on Windows.) Look in the data directory for files with names of the form `host_name.err' and `host_name.log' where `host_name' is the name of your server host. Then check the last few lines of these files: shell> tail host_name.err shell> tail host_name.log If you find something like the following in the log file: 000729 14:50:10 bdb: Recovery function for LSN 1 27595 failed 000729 14:50:10 bdb: warning: ./test/t1.db: No such file or directory 000729 14:50:10 Can't init databases This means that you didn't start `mysqld' with `--bdb-no-recover' and Berkeley DB found something wrong with its log files when it tried to recover your databases. To be able to continue, you should move away the old Berkeley DB log file from the database directory to some other place, where you can later examine these. The log files are named `log.0000000001', where the number will increase over time. If you are running `mysqld' with BDB table support and `mysqld' core dumps at start this could be because of some problems with the BDB recover log. In this case you can try starting `mysqld' with `--bdb-no-recover'. If this helps, then you should remove all `log.*' files from the data directory and try starting `mysqld' again. If you get the following error, it means that some other program (or another `mysqld' server) is already using the TCP/IP port or socket `mysqld' is trying to use: Can't start server: Bind on TCP/IP port: Address already in use or Can't start server : Bind on unix socket... Use `ps' to make sure that you don't have another `mysqld' server running. If you can't find another server running, you can try to execute the command `telnet your-host-name tcp-ip-port-number' and press `RETURN' a couple of times. If you don't get an error message like `telnet: Unable to connect to remote host: Connection refused', something is using the TCP/IP port `mysqld' is trying to use. See *Note mysql_install_db:: and *Note Multiple servers::. If `mysqld' is currently running, you can find out what path settings it is using by executing this command: shell> mysqladmin variables or shell> mysqladmin -h 'your-host-name' variables If `safe_mysqld' starts the server but you can't connect to it, you should make sure you have an entry in `/etc/hosts' that looks like this: 127.0.0.1 localhost This problem occurs only on systems that don't have a working thread library and for which *MySQL* must be configured to use MIT-pthreads. If you can't get `mysqld' to start you can try to make a trace file to find the problem. *Note Making trace files::. If you are using InnoDB tables, refer to the InnoDB-specific startup options. *Note InnoDB start::. If you are using BDB (Berkeley DB) tables, you should familiarize yourself with the different BDB specific startup options. *Note BDB start::. Starting and Stopping MySQL Automatically ----------------------------------------- The `mysql.server' and `safe_mysqld' scripts can be used to start the server automatically at system startup time. `mysql.server' can also be used to stop the server. The `mysql.server' script can be used to start or stop the server by invoking it with `start' or `stop' arguments: shell> mysql.server start shell> mysql.server stop `mysql.server' can be found in the `share/mysql' directory under the *MySQL* installation directory or in the `support-files' directory of the *MySQL* source tree. Before `mysql.server' starts the server, it changes directory to the *MySQL* installation directory, then invokes `safe_mysqld'. You might need to edit `mysql.server' if you have a binary distribution that you've installed in a non-standard location. Modify it to `cd' into the proper directory before it runs `safe_mysqld'. If you want the server to run as some specific user, add an appropriate `user' line to the `/etc/my.cnf' file, as shown later in this section. `mysql.server stop' brings down the server by sending a signal to it. You can take down the server manually by executing `mysqladmin shutdown'. You might want to add these start and stop commands to the appropriate places in your `/etc/rc*' files when you start using *MySQL* for production applications. Note that if you modify `mysql.server', then upgrade *MySQL* sometime, your modified version will be overwritten, so you should make a copy of your edited version that you can reinstall. If your system uses `/etc/rc.local' to start external scripts, you should append the following to it: /bin/sh -c 'cd /usr/local/mysql ; ./bin/safe_mysqld --user=mysql &' You can also add options for `mysql.server' in a global `/etc/my.cnf' file. A typical `/etc/my.cnf' file might look like this: [mysqld] datadir=/usr/local/mysql/var socket=/tmp/mysqld.sock port=3306 user=mysql [mysql.server] basedir=/usr/local/mysql The `mysql.server' script understands the following options: `datadir', `basedir', and `pid-file'. The following table shows which option groups each of the startup scripts read from option files: *Script* *Option groups* `mysqld' `mysqld' and `server' `mysql.server' `mysql.server', `mysqld', and `server' `safe_mysqld' `mysql.server', `mysqld', and `server' *Note Option files::. Upgrading/Downgrading MySQL =========================== You can always move the *MySQL* form and data files between different versions on the same architecture as long as you have the same base version of *MySQL*. The current base version is 3. If you change the character set when running *MySQL* (which may also change the sort order), you must run `myisamchk -r -q' on all tables. Otherwise your indexes may not be ordered correctly. If you are afraid of new versions, you can always rename your old `mysqld' to something like `mysqld'-'old-version-number'. If your new `mysqld' then does something unexpected, you can simply shut it down and restart with your old `mysqld'! When you do an upgrade you should also back up your old databases, of course. If after an upgrade, you experience problems with recompiled client programs, like `Commands out of sync' or unexpected core dumps, you probably have used an old header or library file when compiling your programs. In this case you should check the date for your `mysql.h' file and `libmysqlclient.a' library to verify that they are from the new *MySQL* distribution. If not, please recompile your programs! If you get some problems that the new `mysqld' server doesn't want to start or that you can't connect without a password, check that you don't have some old `my.cnf' file from your old installation! You can check this with: `program-name --print-defaults'. If this outputs anything other than the program name, you have an active `my.cnf' file that will affect things! It is a good idea to rebuild and reinstall the `Msql-Mysql-modules' distribution whenever you install a new release of *MySQL*, particularly if you notice symptoms such as all your `DBI' scripts dumping core after you upgrade *MySQL*. Upgrading From Version 3.22 to Version 3.23 ------------------------------------------- *MySQL* Version 3.23 supports tables of the new `MyISAM' type and the old `ISAM' type. You don't have to convert your old tables to use these with Version 3.23. By default, all new tables will be created with type `MyISAM' (unless you start `mysqld' with the `--default-table-type=isam' option). You can change an `ISAM' table to a `MyISAM' table with `ALTER TABLE table_name TYPE=MyISAM' or the Perl script `mysql_convert_table_format'. Version 3.22 and 3.21 clients will work without any problems with a Version 3.23 server. The following lists tell what you have to watch out for when upgrading to Version 3.23: * All tables that uses the `tis620' character set must be fixed with `myisamchk -r' or `REPAIR TABLE'. * If you do a `DROP DATABASE' on a symbolic linked database, both the link and the original database is deleted. (This didn't happen in 3.22 because configure didn't detect the `readlink' system call). * `OPTIMIZE TABLE' now only works for *MyISAM* tables. For other table types, you can use `ALTER TABLE' to optimize the table. During `OPTIMIZE TABLE' the table is now locked from other threads. * The *MySQL* client `mysql' is now by default started with the option `--no-named-commands (-g)'. This option can be disabled with `--enable-named-commands (-G)'. This may cause incompatibility problems in some cases, for example in SQL scripts that use named commands without a semicolon! Long format commands still work from the first line. * If you are using the `german' character sort order, you must repair all your tables with `isamchk -r', as we have made some changes in the sort order! * The default return type of `IF' will now depend on both arguments and not only the first argument. * `AUTO_INCREMENT' will not work with negative numbers. The reason for this is that negative numbers caused problems when wrapping from -1 to 0. `AUTO_INCREMENT' is now for MyISAM tables handled at a lower level and is much faster than before. For MyISAM tables old numbers are also not reused anymore, even if you delete some rows from the table. * `CASE', `DELAYED', `ELSE', `END', `FULLTEXT', `INNER', `RIGHT', `THEN' and `WHEN' are now reserved words. * `FLOAT(X)' is now a true floating-point type and not a value with a fixed number of decimals. * When declaring `DECIMAL(length,dec)' the length argument no longer includes a place for the sign or the decimal point. * A `TIME' string must now be of one of the following formats: `[[[DAYS] [H]H:]MM:]SS[.fraction]' or `[[[[[H]H]H]H]MM]SS[.fraction]' * `LIKE' now compares strings using the same character comparison rules as `'=''. If you require the old behavior, you can compile *MySQL* with the `CXXFLAGS=-DLIKE_CMP_TOUPPER' flag. * `REGEXP' is now case insensitive for normal (not binary) strings. * When you check/repair tables you should use `CHECK TABLE' or `myisamchk' for `MyISAM' tables (`.MYI') and `isamchk' for ISAM (`.ISM') tables. * If you want your `mysqldump' files to be compatible between *MySQL* Version 3.22 and Version 3.23, you should not use the `--opt' or `--full' option to `mysqldump'. * Check all your calls to `DATE_FORMAT()' to make sure there is a `%' before each format character. (Later *MySQL* Version 3.22 did allow this syntax.) * `mysql_fetch_fields_direct' is now a function (it was a macro) and it returns a pointer to a `MYSQL_FIELD' instead of a `MYSQL_FIELD'. * `mysql_num_fields()' can no longer be used on a `MYSQL*' object (it's now a function that takes `MYSQL_RES*' as an argument. You should now use `mysql_field_count()' instead. * In *MySQL* Version 3.22, the output of `SELECT DISTINCT ...' was almost always sorted. In Version 3.23, you must use `GROUP BY' or `ORDER BY' to obtain sorted output. * `SUM()' now returns `NULL', instead of 0, if there is no matching rows. This is according to ANSI SQL. * An `AND' or `OR' with `NULL' values will now return `NULL' instead of 0. This mostly affects queries that use `NOT' on an `AND/OR' expression as `NOT NULL' = `NULL'. `LPAD()' and `RPAD()' will shorten the result string if it's longer than the length argument. Upgrading from Version 3.21 to Version 3.22 ------------------------------------------- Nothing that affects compatibility has changed between Version 3.21 and 3.22. The only pitfall is that new tables that are created with `DATE' type columns will use the new way to store the date. You can't access these new fields from an old version of `mysqld'. After installing *MySQL* Version 3.22, you should start the new server and then run the `mysql_fix_privilege_tables' script. This will add the new privileges that you need to use the `GRANT' command. If you forget this, you will get `Access denied' when you try to use `ALTER TABLE', `CREATE INDEX', or `DROP INDEX'. If your *MySQL* root user requires a password, you should give this as an argument to `mysql_fix_privilege_tables'. The C API interface to `mysql_real_connect()' has changed. If you have an old client program that calls this function, you must place a `0' for the new `db' argument (or recode the client to send the `db' element for faster connections). You must also call `mysql_init()' before calling `mysql_real_connect()'! This change was done to allow the new `mysql_options()' function to save options in the `MYSQL' handler structure. The `mysqld' variable `key_buffer' has changed names to `key_buffer_size', but you can still use the old name in your startup files. Upgrading from Version 3.20 to Version 3.21 ------------------------------------------- If you are running a version older than Version 3.20.28 and want to switch to Version 3.21, you need to do the following: You can start the `mysqld' Version 3.21 server with `safe_mysqld --old-protocol' to use it with clients from a Version 3.20 distribution. In this case, the new client function `mysql_errno()' will not return any server error, only `CR_UNKNOWN_ERROR' (but it works for client errors), and the server uses the old `password()' checking rather than the new one. If you are *NOT* using the `--old-protocol' option to `mysqld', you will need to make the following changes: * All client code must be recompiled. If you are using ODBC, you must get the new *MyODBC* 2.x driver. * The script `scripts/add_long_password' must be run to convert the `Password' field in the `mysql.user' table to `CHAR(16)'. * All passwords must be reassigned in the `mysql.user' table (to get 62-bit rather than 31-bit passwords). * The table format hasn't changed, so you don't have to convert any tables. *MySQL* Version 3.20.28 and above can handle the new `user' table format without affecting clients. If you have a *MySQL* version earlier than Version 3.20.28, passwords will no longer work with it if you convert the `user' table. So to be safe, you should first upgrade to at least Version 3.20.28 and then upgrade to Version 3.21. The new client code works with a 3.20.x `mysqld' server, so if you experience problems with 3.21.x, you can use the old 3.20.x server without having to recompile the clients again. If you are not using the `--old-protocol' option to `mysqld', old clients will issue the error message: ERROR: Protocol mismatch. Server Version = 10 Client Version = 9 The new Perl `DBI'/`DBD' interface also supports the old `mysqlperl' interface. The only change you have to make if you use `mysqlperl' is to change the arguments to the `connect()' function. The new arguments are: `host', `database', `user', `password' (the `user' and `password' arguments have changed places). *Note Perl `DBI' Class: Perl DBI Class. The following changes may affect queries in old applications: * `HAVING' must now be specified before any `ORDER BY' clause. * The parameters to `LOCATE()' have been swapped. * There are some new reserved words. The most notable are `DATE', `TIME', and `TIMESTAMP'. Upgrading to Another Architecture --------------------------------- If you are using *MySQL* Version 3.23, you can copy the `.frm', `.MYI', and `.MYD' files between different architectures that support the same floating-point format. (*MySQL* takes care of any byte swapping issues.) The *MySQL* `ISAM' data and index files (`.ISD' and `*.ISM', respectively) are architecture-dependent and in some cases OS-dependent. If you want to move your applications to another machine that has a different architecture or OS than your current machine, you should not try to move a database by simply copying the files to the other machine. Use `mysqldump' instead. By default, `mysqldump' will create a file full of SQL statements. You can then transfer the file to the other machine and feed it as input to the `mysql' client. Try `mysqldump --help' to see what options are available. If you are moving the data to a newer version of *MySQL*, you should use `mysqldump --opt' with the newer version to get a fast, compact dump. The easiest (although not the fastest) way to move a database between two machines is to run the following commands on the machine on which the database is located: shell> mysqladmin -h 'other hostname' create db_name shell> mysqldump --opt db_name \ | mysql -h 'other hostname' db_name If you want to copy a database from a remote machine over a slow network, you can use: shell> mysqladmin create db_name shell> mysqldump -h 'other hostname' --opt --compress db_name \ | mysql db_name You can also store the result in a file, then transfer the file to the target machine and load the file into the database there. For example, you can dump a database to a file on the source machine like this: shell> mysqldump --quick db_name | gzip > db_name.contents.gz (The file created in this example is compressed.) Transfer the file containing the database contents to the target machine and run these commands there: shell> mysqladmin create db_name shell> gunzip < db_name.contents.gz | mysql db_name You can also use `mysqldump' and `mysqlimport' to accomplish the database transfer. For big tables, this is much faster than simply using `mysqldump'. In the commands shown below, `DUMPDIR' represents the full pathname of the directory you use to store the output from `mysqldump'. First, create the directory for the output files and dump the database: shell> mkdir DUMPDIR shell> mysqldump --tab=DUMPDIR db_name Then transfer the files in the `DUMPDIR' directory to some corresponding directory on the target machine and load the files into *MySQL* there: shell> mysqladmin create db_name # create database shell> cat DUMPDIR/*.sql | mysql db_name # create tables in database shell> mysqlimport db_name DUMPDIR/*.txt # load data into tables Also, don't forget to copy the `mysql' database, because that's where the grant tables (`user', `db', `host') are stored. You may have to run commands as the *MySQL* `root' user on the new machine until you have the `mysql' database in place. After you import the `mysql' database on the new machine, execute `mysqladmin flush-privileges' so that the server reloads the grant table information. Operating System Specific Notes =============================== Linux Notes (All Linux Versions) -------------------------------- The notes below regarding *glibc* apply only to the situation when you build *MySQL* yourself. If you are running Linux on an x86 machine, in most cases it is much better for you to just use our binary. We link our binaries against the best patched version of *glibc* we can come up with and with the best compiler options, in an attempt to make it suitable for a high-load server. So if you read the text below, and are in doubt about what you should do, try our binary first to see if it meets your needs, and worry about your own build only after you have discovered that our binary is not good enough. In that case, we would appreciate a note about it, so we can build a better binary next time. For a typical user, even for setups with a lot of concurrent connections and/or tables exceeding 2GB limit, our binary in most cases is the best choice. *MySQL* uses LinuxThreads on Linux. If you are using an old Linux version that doesn't have `glibc2', you must install LinuxThreads before trying to compile *MySQL*. You can get LinuxThreads at `http://www.mysql.com/Downloads/Linux'. *NOTE:* We have seen some strange problems with Linux 2.2.14 and *MySQL* on SMP systems; If you have a SMP system, we recommend you to upgrade to Linux 2.4 ASAP! Your system will be faster and more stable by doing this! Note that `glibc' versions before and including Version 2.1.1 have a fatal bug in `pthread_mutex_timedwait' handling, which is used when you do `INSERT DELAYED'. We recommend you to not use `INSERT DELAYED' before upgrading glibc. If you plan to have 1000+ concurrent connections, you will need to make some changes to LinuxThreads, recompile it, and relink *MySQL* against the new `libpthread.a'. Increase `PTHREAD_THREADS_MAX' in `sysdeps/unix/sysv/linux/bits/local_lim.h' to 4096 and decrease `STACK_SIZE' in `linuxthreads/internals.h' to 256 KB. The paths are relative to the root of `glibc' Note that *MySQL* will not be stable with around 600-1000 connections if `STACK_SIZE' is the default of 2 MB. If you have a problem with that *MySQL* can't open enough files, or connections, it may be that you haven't configured Linux to handle enough files. In Linux 2.2 and forwards, you can check the number of allocated file handlers by doing: cat /proc/sys/fs/file-max cat /proc/sys/fs/dquot-max cat /proc/sys/fs/super-max If you have more than 16M of memory, you should add something like the following in your boot script (`/etc/rc/boot.local' on SuSE): echo 65536 > /proc/sys/fs/file-max echo 8192 > /proc/sys/fs/dquot-max echo 1024 > /proc/sys/fs/super-max You can also run the above from the command line as root, but in this case your old limits will be used next time your computer reboots. You should also add /etc/my.cnf: [safe_mysqld] open-files-limit=8192 The above should allow *MySQL* to create up to 8192 connections + files. The `STACK_SIZE' constant in LinuxThreads controls the spacing of thread stacks in the address space. It needs to be large enough so that there will be plenty of room for the stack of each individual thread, but small enough to keep the stack of some thread from running into the global `mysqld' data. Unfortunately, the Linux implementation of `mmap()', as we have experimentally discovered, will successfully unmap an already mapped region if you ask it to map out an address already in use, zeroing out the data on the entire page, instead of returning an error. So, the safety of `mysqld' or any other threaded application depends on the "gentleman" behavior of the code that creates threads. The user must take measures to make sure the number of running threads at any time is sufficiently low for thread stacks to stay away from the global heap. With `mysqld', you should enforce this "gentleman" behavior by setting a reasonable value for the `max_connections' variable. If you build *MySQL* yourself and do not what to mess with patching LinuxThreads, you should set `max_connections' to a value no higher than 500. It should be even less if you have a large key buffer, large heap tables, or some other things that make *mysqld* allocate a lot of memory or if you are running a 2.2 kernel with a 2GB patch. If you are using our binary or RPM version 3.23.25 or later, you can safely set `max_connections' at 1500, assuming no large key buffer or heap tables with lots of data. The more you reduce `STACK_SIZE' in LinuxThreads the more threads you can safely create. We recommend the values between 128K and 256K. If you use a lot of concurrent connections, you may suffer from a "feature" in the 2.2 kernel that penalizes a process for forking or cloning a child in an attempt to prevent a fork bomb attack. This will cause *MySQL* not to scale well as you increase the number of concurrent clients. On single CPU systems, we have seen this manifested in a very slow thread creation, which means it may take a long time to connect to *MySQL* (as long as 1 minute), and it may take just as long to shut it down. On multiple CPU systems, we have observed a gradual drop in query speed as the number of clients increases. In the process of trying to find a solution, we have received a kernel patch from one of our users, who claimed it made a lot of difference for his site. The patch is available here (`http://www.mysql.com/Downloads/Patches/linux-fork.patch'). We have now done rather extensive testing of this patch on both development and production systems. It has significantly improved `MySQL' performance without causing any problems and we now recommend it to our users who are still running high-load servers on 2.2 kernels. This issue has been fixed in the 2.4 kernel, so if you are not satisfied with the current performance of your system, rather than patching your 2.2 kernel, it might be easier to just upgrade to 2.4, which will also give you a nice SMP boost in addition to fixing this fairness bug. We have tested *MySQL* on the 2.4 kernel on a 2 CPU machine and found *MySQL* scales MUCH better - there was virtually no slowdown on query throughput all the way up to 1000 clients, and *MySQL* scaling factor ( computed as the ratio of maximum throughput to the throughput with one client) was 180%. We have observed similar results on a 4-CPU system - virtually no slowdown as the number of clients was increased up to 1000, and 300% scaling factor. So for a high-load SMP server we would definitely recommend the 2.4 kernel at this point. We have discovered that it is essential to run `mysqld' process with the highest possible priority on the 2.4 kernel to achieve maximum performance. This can be done by adding `renice -20 $$' command to `safe_mysqld'. In our testing on a 4-CPU machine, increasing the priority gave 60% increase in throughput with 400 clients. We are currently also trying to collect more info on how well `MySQL' performs on 2.4 kernel on 4-way and 8-way systems. If you have access such a system and have done some benchmarks, please send a mail to with the results - we will include them in the manual. There is another issue that greatly hurts *MySQL* performance, especially on SMP systems. The implementation of mutex in LinuxThreads in *glibc-2.1* is very bad for programs with many threads that only hold the mutex for a short time. On an SMP system, ironic as it is, if you link *MySQL* against unmodified *LinuxThreads*, removing processors from the machine improves *MySQL* performance in many cases. We have made a patch available for *glibc 2.1.3*, linuxthreads-2.1-patch (http://www.mysql.com/Downloads/Linux/linuxthreads-2.1-patch) to correct this behavior. With *glibc-2.2.2* *MySQL* version 3.23.36 will use the adaptive mutex, which is much better than even the patched one in *glibc-2.1.3*. Be warned, however, that under some conditions, the current mutex code in *glibc-2.2.2* overspins, which hurts *MySQL* performance. The chance of this condition can be reduced by renicing `mysqld' process to the highest priority. We have also been able to correct the overspin behavior with a patch, available here (http://www.mysql.com/Downloads/Linux/linuxthreads-2.2.2.patch). It combines the correction of overspin, maximum number of threads, and stack spacing all in one. You will need to apply it in the `linuxthreads' directory with `patch -p0 cp support-files/mysql.server /etc/init.d/mysql.server shell> /usr/sbin/update-rc.d mysql.server defaults 99 `mysql.server' can be found in the `share/mysql' directory under the *MySQL* installation directory or in the `support-files' directory of the *MySQL* source tree. If `mysqld' always core dumps when it starts up, the problem may be that you have an old `/lib/libc.a'. Try renaming it, then remove `sql/mysqld' and do a new `make install' and try again. This problem has been reported on some Slackware installations. If you get the following error when linking `mysqld', it means that your `libg++.a' is not installed correctly: /usr/lib/libc.a(putc.o): In function `_IO_putc': putc.o(.text+0x0): multiple definition of `_IO_putc' You can avoid using `libg++.a' by running `configure' like this: shell> CXX=gcc ./configure Linux SPARC Notes ................. In some implementations, `readdir_r()' is broken. The symptom is that `SHOW DATABASES' always returns an empty set. This can be fixed by removing `HAVE_READDIR_R' from `config.h' after configuring and before compiling. Some problems will require patching your Linux installation. The patch can be found at `http://www.mysql.com/Downloads/patches/Linux-sparc-2.0.30.diff'. This patch is against the Linux distribution `sparclinux-2.0.30.tar.gz' that is available at `vger.rutgers.edu' (a version of Linux that was never merged with the official 2.0.30). You must also install LinuxThreads Version 0.6 or newer. Linux Alpha Notes ................. *MySQL* Version 3.23.12 is the first *MySQL* version that is tested on Linux-Alpha. If you plan to use *MySQL* on Linux-Alpha, you should ensure that you have this version or newer. We have tested *MySQL* on Alpha with our benchmarks and test suite, and it appears to work nicely. The main thing we haven't yet had time to test is how things works with many concurrent users. When we compiled the standard *MySQL* binary we are using SuSE 6.4, kernel 2.2.13-SMP, Compaq C compiler (V6.2-504) and Compaq C++ compiler (V6.3-005) on a Comaq DS20 machine with an Alpha EV6 processor. You can find the above compilers at `http://www.support.compaq.com/alpha-tools'). By using these compilers, instead of gcc, we get about 9-14 % better performance with *MySQL*. Note that the configure line optimized the binary for the current CPU; This means you can only use our binary if you have an Alpha EV6 processor. We also compile statically to avoid library problems. CC=ccc CFLAGS="-fast" CXX=cxx CXXFLAGS="-fast -noexceptions -nortti" ./configure --prefix=/usr/local/mysql --disable-shared --with-extra-charsets=complex --enable-thread-safe-client --with-mysqld-ldflags=-non_shared --with-client-ldflags=-non_shared If you want to use egcs the following configure line worked for us: CFLAGS="-O3 -fomit-frame-pointer" CXX=gcc CXXFLAGS="-O3 -fomit-frame-pointer -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --disable-shared Some known problems when running *MySQL* on Linux-Alpha: * Debugging threaded applications like *MySQL* will not work with `gdb 4.18'. You should download and use gdb 5.0 instead! * If you try linking `mysqld' statically when using `gcc', the resulting image will core dump at start. In other words, *DON'T* use `--with-mysqld-ldflags=-all-static' with `gcc'. Linux PowerPC Notes ................... *MySQL* should work on MkLinux with the newest `glibc' package (tested with `glibc' 2.0.7). Linux MIPS Notes ................ To get *MySQL* to work on Qube2, (Linux Mips), you need the newest `glibc' libraries (`glibc-2.0.7-29C2' is known to work). You must also use the `egcs' C++ compiler (`egcs-1.0.2-9', `gcc 2.95.2' or newer). Linux IA64 Notes ................ To get *MySQL* to compile on Linux Ia64, we had to do the following (we assume that this will be easier when next gcc version for ia64 is released). Using `gcc-2.9-final': CFLAGS="-O2" CXX=gcc CXXFLAGS="-O2 -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static --disable-shared --with-extra-charsets=complex After `make' you will get an error that `sql/opt_range.cc' will not compile (internal compiler error). To fix this, go to the sql directory and type `make' again. Copy the compile line, but change -O2 to -O0. The file should now compile. Now you can do: cd .. make make_install and *mysqld* should be ready to run. Windows Notes ------------- This section describes installation and use of *MySQL* on Windows. This information is also provided in the `README' file that comes with the *MySQL* Windows distribution. Starting MySQL on Windows 95 or Windows 98 .......................................... *MySQL* uses TCP/IP to connect a client to a server. (This will allow any machine on your network to connect to your *MySQL* server.) Because of this, you must install TCP/IP on your machine before starting *MySQL*. You can find TCP/IP on your Windows CD-ROM. Note that if you are using an old Win95 release (for example OSR2), it's likely that you have an old Winsock package! *MySQL* requires Winsock 2! You can get the newest Winsock from `http://www.microsoft.com/'. Win98 has the new Winsock 2 library, so the above doesn't apply for Win98. To start the `mysqld' server, you should start an MS-DOS window and type: C:\> C:\mysql\bin\mysqld This will start `mysqld' in the background without a window. You can kill the *MySQL* server by executing: C:\> C:\mysql\bin\mysqladmin -u root shutdown Note that Win95 and Win98 don't support creation of named pipes. On Win95 and Win98, you can only use named pipes to connect to a remote *MySQL* server running on a Windows NT server host. (The *MySQL* server must also support named pipes, of course. For example, using `mysqld-opt' under NT will not allow named pipe connections. You should use either `mysqld-nt' or `mysqld-max-nt'.) If `mysqld' doesn't start, please check the `\mysql\data\mysql.err' file to see if the server wrote any message there to indicate the cause of the problem. You can also try to start the server with `mysqld --standalone'; In this case, you may get some useful information on the screen that may help solve the problem. The last option is to start `mysqld' with `--standalone --debug'. In this case `mysqld' will write a log file `C:\mysqld.trace' that should contain the reason why `mysqld' doesn't start. *Note Making trace files::. Starting MySQL on Windows NT or Windows 2000 ............................................ The Win95/Win98 section also applies to *MySQL* on NT/Win2000, with the following differences: To get *MySQL* to work with TCP/IP on NT, you must install service pack 3 (or newer)! Note that everything in the following that applies for NT also applies for Win2000! For NT/Win2000, the server name is `mysqld-nt'. Normally you should install *MySQL* as a service on NT/Win2000: C:\> C:\mysql\bin\mysqld-nt --install or C:\> C:\mysql\bin\mysqld-max-nt --install (Under Windows NT, you can actually install any of the server binaries as a service, but only those having names that end with `-nt.exe' provide support for named pipes.) You can start and stop the *MySQL* service with these commands: C:\> NET START mysql C:\> NET STOP mysql Note that in this case you can't use any other options for `mysqld-nt'! You can also run `mysqld-nt' as a stand-alone program on NT if you need to start `mysqld-nt' with any options! If you start `mysqld-nt' without options on NT, `mysqld-nt' tries to start itself as a service with the default service options. If you have stopped `mysqld-nt', you have to start it with `NET START mysql'. The service is installed with the name `MySQL'. Once installed, it must be started using the Services Control Manager (SCM) Utility found in the Control Panel, or by using the `NET START MySQL' command. If any options are desired, they must be specified as "Startup parameters" in the SCM utility before you start the *MySQL* service. Once running, `mysqld-nt' can be stopped using `mysqladmin', or from the SCM utility or by using the command `NET STOP MySQL'. If you use SCM to stop `mysqld-nt', there is a strange message from SCM about `mysqld shutdown normally'. When run as a service, `mysqld-nt' has no access to a console and so no messages can be seen. On NT you can get the following service error messages: Permission Denied Means that it cannot find `mysqld-nt.exe'. Cannot Register Means that the path is incorrect. Failed to install Means that the service is already installed or service. that the Service Control Manager is in bad state. If you have problems installing `mysqld-nt' as a service, try starting it with the full path: C:\> C:\mysql\bin\mysqld-nt --install If this doesn't work, you can get `mysqld-nt' to start properly by fixing the path in the registry! If you don't want to start `mysqld-nt' as a service, you can start it as follows: C:\> C:\mysql\bin\mysqld-nt --standalone or C:\> C:\mysql\bin\mysqld --standalone --debug The last version gives you a debug trace in `C:\mysqld.trace'. *Note Making trace files::. Running MySQL on Windows ........................ *MySQL* supports TCP/IP on all Windows platforms and named pipes on NT. The default is to use named pipes for local connections on NT and TCP/IP for all other cases if the client has TCP/IP installed. The host name specifies which protocol is used: *Host name* *Protocol* NULL (none) On NT, try named pipes first; if that doesn't work, use TCP/IP. On Win95/Win98, TCP/IP is used. . Named pipes localhost TCP/IP to current host hostname TCP/IP You can force a *MySQL* client to use named pipes by specifying the `--pipe' option or by specifying `.' as the host name. Use the `--socket' option to specify the name of the pipe. You can test whether or not *MySQL* is working by executing the following commands: C:\> C:\mysql\bin\mysqlshow C:\> C:\mysql\bin\mysqlshow -u root mysql C:\> C:\mysql\bin\mysqladmin version status proc C:\> C:\mysql\bin\mysql test If `mysqld' is slow to answer to connections on Win95/Win98, there is probably a problem with your DNS. In this case, start `mysqld' with `--skip-name-resolve' and use only `localhost' and IP numbers in the *MySQL* grant tables. You can also avoid DNS when connecting to a `mysqld-nt' *MySQL* server running on NT by using the `--pipe' argument to specify use of named pipes. This works for most *MySQL* clients. There are two versions of the *MySQL* command-line tool: `mysql' Compiled on native Windows, which offers very limited text editing capabilities. `mysqlc' Compiled with the Cygnus GNU compiler and libraries, which offers `readline' editing. If you want to use `mysqlc.exe', you must copy `C:\mysql\lib\cygwinb19.dll' to your Windows system directory (`\windows\system' or similar place). The default privileges on Windows give all local users full privileges to all databases without specifying a password. To make *MySQL* more secure, you should set a password for all users and remove the row in the `mysql.user' table that has `Host='localhost'' and `User='''. You should also add a password for the `root' user. The following example starts by removing the anonymous user that can be used by anyone to access the `test' database, then sets a `root' user password: C:\> C:\mysql\bin\mysql mysql mysql> DELETE FROM user WHERE Host='localhost' AND User=''; mysql> QUIT C:\> C:\mysql\bin\mysqladmin reload C:\> C:\mysql\bin\mysqladmin -u root password your_password After you've set the password, if you want to take down the `mysqld' server, you can do so using this command: C:\> mysqladmin --user=root --password=your_password shutdown If you are using the old shareware version of *MySQL* Version 3.21 under Windows, the above command will fail with an error: `parse error near 'SET OPTION password''. The fix is in to upgrade to the current *MySQL* version, which is freely available. With the current *MySQL* versions you can easily add new users and change privileges with `GRANT' and `REVOKE' commands. *Note GRANT::. Connecting to a Remote MySQL from Windows with SSH .................................................. Here is a note about how to connect to get a secure connection to remote *MySQL* server with SSH (by David Carlson ): * Install an SSH client on your Windows machine. As a user, the best non-free one I've found is from `SecureCRT' from `http://www.vandyke.com/'. Another option is `f-secure' from `http://www.f-secure.com/'. You can also find some free ones on *Google* at `http://directory.google.com/Top/Computers/Security/Products_and_Tools/Cryptography/SSH/Clients/Windows/'. * Start your Windows SSH client. Set `Host_Name = yourmysqlserver_URL_or_IP'. Set `userid=your_userid' to log in to your server (probably not the same as your *MySQL* login/password. * Set up port forwarding. Either do a remote forward (Set `local_port: 3306', `remote_host: yourmysqlservername_or_ip', `remote_port: 3306' ) or a local forward (Set `port: 3306', `host: localhost', `remote port: 3306'). * Save everything, otherwise you'll have to redo it the next time. * Log in to your server with SSH session you just created. * On your Windows machine, start some ODBC application (such as Access). * Create a new file in Windows and link to *MySQL* using the ODBC driver the same way you normally do, EXCEPT type in `localhost' for the *MySQL* host server -- not `yourmysqlservername'. You should now have an ODBC connection to *MySQL*, encrypted using SSH. Splitting Data Across Different Disks on Windows ................................................ Beginning with *MySQL* Version 3.23.16, the `mysqld-max' and `mysql-max-nt' servers in the *MySQL* distribution are compiled with the `-DUSE_SYMDIR' option. This allows you to put a database on different disk by adding a symbolic link to it (in a manner similar to the way that symbolic links work on Unix). On Windows, you make a symbolic link to a database by creating a file that contains the path to the destination directory and saving this in the `mysql_data' directory under the filename `database.sym'. Note that the symbolic link will be used only if the directory `mysql_data_dir\database' doesn't exist. For example, if the *MySQL* data directory is `C:\mysql\data' and you want to have database `foo' located at `D:\data\foo', you should create the file `C:\mysql\data\foo.sym' that contains the text `D:\data\foo\'. After that, all tables created in the database `foo' will be created in `D:\data\foo'. Note that because of the speed penalty you get when opening every table, we have not enabled this by default even if you have compiled *MySQL* with support for this. To enable symlinks you should put in your `my.cnf' or `my.ini' file the following entry: [mysqld] use-symbolic-links In *MySQL* 4.0 we will enable symlinks by default. Then you should instead use the `skip-symlink' option if you want to disable this. Compiling MySQL Clients on Windows .................................. In your source files, you should include `windows.h' before you include `mysql.h': #if defined(_WIN32) || defined(_WIN64) #include #endif #include You can either link your code with the dynamic `libmysql.lib' library, which is just a wrapper to load in `libmysql.dll' on demand, or link with the static `mysqlclient.lib' library. Note that as the mysqlclient libraries are compiled as threaded libraries, you should also compile your code to be multi-threaded! MySQL-Windows Compared to Unix MySQL .................................... *MySQL*-Windows has by now proven itself to be very stable. This version of *MySQL* has the same features as the corresponding Unix version with the following exceptions: *Win95 and threads* Win95 leaks about 200 bytes of main memory for each thread creation. Each connection in *MySQL* creates a new thread, so you shouldn't run `mysqld' for an extended time on Win95 if your server handles many connections! WinNT and Win98 don't suffer from this bug. *Concurrent reads* *MySQL* depends on the `pread()' and `pwrite()' calls to be able to mix `INSERT' and `SELECT'. Currently we use mutexes to emulate `pread()'/`pwrite()'. We will, in the long run, replace the file level interface with a virtual interface so that we can use the `readfile()'/`writefile()' interface on NT to get more speed. The current implementation limits the number of open files *MySQL* can use to 1024, which means that you will not be able to run as many concurrent threads on NT as on Unix. *Blocking read* *MySQL* uses a blocking read for each connection. This means that: * A connection will not be disconnected automatically after 8 hours, as happens with the Unix version of *MySQL*. * If a connection hangs, it's impossible to break it without killing *MySQL*. * `mysqladmin kill' will not work on a sleeping connection. * `mysqladmin shutdown' can't abort as long as there are sleeping connections. We plan to fix this problem when our Windows developers have figured out a nice workaround. *UDF functions* For the moment, *MySQL*-Windows does not support user-definable functions. *`DROP DATABASE'* You can't drop a database that is in use by some thread. *Killing *MySQL* from the task manager* You can't kill *MySQL* from the task manager or with the shutdown utility in Win95. You must take it down with `mysqladmin shutdown'. *Case-insensitive names* Filenames are case insensitive on Windows, so database and table names are also case insensitive in *MySQL* for Windows. The only restriction is that database and table names must be specified using the same case throughout a given statement. *Note Name case sensitivity::. *The `\' directory character* Pathname components in Win95 are separated by the `\' character, which is also the escape character in *MySQL*. If you are using `LOAD DATA INFILE' or `SELECT ... INTO OUTFILE', you must double the `\' character: mysql> LOAD DATA INFILE "C:\\tmp\\skr.txt" INTO TABLE skr; mysql> SELECT * INTO OUTFILE 'C:\\tmp\\skr.txt' FROM skr; Alternatively, use Unix style filenames with `/' characters: mysql> LOAD DATA INFILE "C:/tmp/skr.txt" INTO TABLE skr; mysql> SELECT * INTO OUTFILE 'C:/tmp/skr.txt' FROM skr; *`Can't open named pipe' error* If you use a *MySQL* 3.22 version on NT with the newest mysql-clients you will get the following error: error 2017: can't open named pipe to host: . pipe... This is because the release version of *MySQL* uses named pipes on NT by default. You can avoid this error by using the `--host=localhost' option to the new *MySQL* clients or create an option file `C:\my.cnf' that contains the following information: [client] host = localhost *`Access denied for user' error* If you get the error `Access denied for user: 'some-user@unknown' to database 'mysql'' when accessing a *MySQL* server on the same machine, this means that *MySQL* can't resolve your host name properly. To fix this, you should create a file `\windows\hosts' with the following information: 127.0.0.1 localhost *`ALTER TABLE'* While you are executing an `ALTER TABLE' statement, the table is locked from usage by other threads. This has to do with the fact that on Windows, you can't delete a file that is in use by another threads. (In the future, we may find some way to work around this problem.) *`DROP TABLE' on a table that is in use by a `MERGE' table will not work* The `MERGE' handler does its table mapping hidden from *MySQL*. Because Windows doesn't allow you to drop files that are open, you first must flush all `MERGE' tables (with `FLUSH TABLES') or drop the `MERGE' table before dropping the table. We will fix this at the same time we introduce `VIEW's. Here are some open issues for anyone who might want to help us with the Windows release: * Make a single-user `MYSQL.DLL' server. This should include everything in a standard *MySQL* server, except thread creation. This will make *MySQL* much easier to use in applications that don't need a true client/server and don't need to access the server from other hosts. * Add some nice start and shutdown icons to the *MySQL* installation. * Create a tool to manage registry entries for the *MySQL* startup options. The registry entry reading is already coded into `mysqld.cc', but it should be recoded to be more parameter oriented. The tool should also be able to update the `C:\my.cnf' option file if the user prefers to use that instead of the registry. * When registering `mysqld' as a service with `--install' (on NT) it would be nice if you could also add default options on the command line. For the moment, the workaround is to list the parameters in the `C:\my.cnf' file instead. * It would be real nice to be able to kill `mysqld' from the task manager. For the moment, you must use `mysqladmin shutdown'. * Port `readline' to Windows for use in the `mysql' command line tool. * GUI versions of the standard *MySQL* clients (`mysql', `mysqlshow', `mysqladmin', and `mysqldump') would be nice. * It would be nice if the socket read and write functions in `net.c' were interruptible. This would make it possible to kill open threads with `mysqladmin kill' on Windows. * `mysqld' always starts in the "C" locale and not in the default locale. We would like to have `mysqld' use the current locale for the sort order. * Implement UDF functions with `.DLL's. * Add macros to use the faster thread-safe increment/decrement methods provided by Windows. Other Windows-specific issues are described in the `README' file that comes with the *MySQL*-Windows distribution. Solaris Notes ------------- On Solaris, you may run into trouble even before you get the *MySQL* distribution unpacked! Solaris `tar' can't handle long file names, so you may see an error like this when you unpack *MySQL*: x mysql-3.22.12-beta/bench/Results/ATIS-mysql_odbc-NT_4.0-cmp-db2,informix,ms-sql,mysql,oracle,solid,sybase, 0 bytes, 0 tape blocks tar: directory checksum error In this case, you must use GNU `tar' (`gtar') to unpack the distribution. You can find a precompiled copy for Solaris at `http://www.mysql.com/Downloads/'. Sun native threads work only on Solaris 2.5 and higher. For Version 2.4 and earlier, *MySQL* will automatically use MIT-pthreads. *Note MIT-pthreads::. If you get the following error from configure: checking for restartable system calls... configure: error can not run test programs while cross compiling This means that you have something wrong with your compiler installation! In this case you should upgrade your compiler to a newer version. You may also be able to solve this problem by inserting the following row into the `config.cache' file: ac_cv_sys_restartable_syscalls=${ac_cv_sys_restartable_syscalls='no'} If you are using Solaris on a SPARC, the recommended compiler is `gcc' 2.95.2. You can find this at `http://gcc.gnu.org/'. Note that `egcs' 1.1.1 and `gcc' 2.8.1 don't work reliably on SPARC! The recommended `configure' line when using `gcc' 2.95.2 is: CC=gcc CFLAGS="-O3" \ CXX=gcc CXXFLAGS="-O3 -felide-constructors -fno-exceptions -fno-rtti" \ ./configure --prefix=/usr/local/mysql --with-low-memory --enable-assembler If you have a ultra sparc, you can get 4 % more performance by adding "-mcpu=v8 -Wa,-xarch=v8plusa" to CFLAGS and CXXFLAGS. If you have the Sun Workshop (SunPro) 4.2 (or newer) compiler, you can run `configure' like this: CC=cc CFLAGS="-Xa -fast -xO4 -native -xstrconst -mt" \ CXX=CC CXXFLAGS="-noex -xO4 -mt" \ ./configure --prefix=/usr/local/mysql --enable-assembler You may also have to edit the `configure' script to change this line: #if !defined(__STDC__) || __STDC__ != 1 to this: #if !defined(__STDC__) If you turn on `__STDC__' with the `-Xc' option, the Sun compiler can't compile with the Solaris `pthread.h' header file. This is a Sun bug (broken compiler or broken include file). If `mysqld' issues the error message shown below when you run it, you have tried to compile *MySQL* with the Sun compiler without enabling the multi-thread option (`-mt'): libc internal error: _rmutex_unlock: rmutex not held Add `-mt' to `CFLAGS' and `CXXFLAGS' and try again. If you get the following error when compiling *MySQL* with `gcc', it means that your `gcc' is not configured for your version of Solaris: shell> gcc -O3 -g -O2 -DDBUG_OFF -o thr_alarm ... ./thr_alarm.c: In function `signal_hand': ./thr_alarm.c:556: too many arguments to function `sigwait' The proper thing to do in this case is to get the newest version of `gcc' and compile it with your current `gcc' compiler! At least for Solaris 2.5, almost all binary versions of `gcc' have old, unusable include files that will break all programs that use threads (and possibly other programs)! Solaris doesn't provide static versions of all system libraries (`libpthreads' and `libdl'), so you can't compile *MySQL* with `--static'. If you try to do so, you will get the error: ld: fatal: library -ldl: not found or undefined reference to `dlopen' If too many processes try to connect very rapidly to `mysqld', you will see this error in the *MySQL* log: Error in accept: Protocol error You might try starting the server with the `--set-variable back_log=50' option as a workaround for this. *Note Command-line options::. If you are linking your own *MySQL* client, you might get the following error when you try to execute it: ld.so.1: ./my: fatal: libmysqlclient.so.#: open failed: No such file or directory The problem can be avoided by one of the following methods: * Link the client with the following flag (instead of `-Lpath'): `-Wl,r/full-path-to-libmysqlclient.so'. * Copy `libmysqclient.so' to `/usr/lib'. * Add the pathname of the directory where `libmysqlclient.so' is located to the `LD_RUN_PATH' environment variable before running your client. When using the `--with-libwrap' configure option, you must also include the libraries that `libwrap.a' needs: --with-libwrap="/opt/NUtcpwrapper-7.6/lib/libwrap.a -lnsl -lsocket If you have problems with configure trying to link with `-lz' and you don't have `zlib' installed, you have two options: * If you want to be able to use the compressed communication protocol, you need to get and install zlib from ftp.gnu.org. * Configure with `--with-named-z-libs=no'. If you are using gcc and have problems with loading `UDF' functions into *MySQL*, try adding `-lgcc' to the link line for the `UDF' function. If you would like *MySQL* to start automatically, you can copy `support-files/mysql.server' to `/etc/init.d' and create a symbolic link to it named `/etc/rc3.d/S99mysql.server'. Solaris 2.7/2.8 Notes ..................... You can normally use a Solaris 2.6 binary on Solaris 2.7 and 2.8. Most of the Solaris 2.6 issues also apply for Solaris 2.7 and 2.8. Note that *MySQL* Version 3.23.4 and above should be able to autodetect new versions of Solaris and enable workarounds for the following problems! Solaris 2.7 / 2.8 has some bugs in the include files. You may see the following error when you use `gcc': /usr/include/widec.h:42: warning: `getwc' redefined /usr/include/wchar.h:326: warning: this is the location of the previous definition If this occurs, you can do the following to fix the problem: Copy `/usr/include/widec.h' to `.../lib/gcc-lib/os/gcc-version/include' and change line 41 from: #if !defined(lint) && !defined(__lint) to #if !defined(lint) && !defined(__lint) && !defined(getwc) Alternatively, you can edit `/usr/include/widec.h' directly. Either way, after you make the fix, you should remove `config.cache' and run `configure' again! If you get errors like this when you run `make', it's because `configure' didn't detect the `curses.h' file (probably because of the error in `/usr/include/widec.h'): In file included from mysql.cc:50: /usr/include/term.h:1060: syntax error before `,' /usr/include/term.h:1081: syntax error before `;' The solution to this is to do one of the following: * Configure with `CFLAGS=-DHAVE_CURSES_H CXXFLAGS=-DHAVE_CURSES_H ./configure'. * Edit `/usr/include/widec.h' as indicted above and rerun configure. * Remove the `#define HAVE_TERM' line from `config.h' file and run `make' again. If you get a problem that your linker can't find `-lz' when linking your client program, the problem is probably that your `libz.so' file is installed in `/usr/local/lib'. You can fix this by one of the following methods: * Add `/usr/local/lib' to `LD_LIBRARY_PATH'. * Add a link to `libz.so' from `/lib'. * If you are using Solaris 8, you can install the optional zlib from your Solaris 8 CD distribution. * Configure *MySQL* with the `--with-named-z-libs=no' option. Solaris x86 Notes ................. On Solaris 2.8 on x86, *mysqld* will core dump if you run 'strip' in. If you are using `gcc' or `egcs' on Solaris x86 and you experience problems with core dumps under load, you should use the following `configure' command: CC=gcc CFLAGS="-O3 -fomit-frame-pointer -DHAVE_CURSES_H" \ CXX=gcc \ CXXFLAGS="-O3 -fomit-frame-pointer -felide-constructors -fno-exceptions -fno-rtti -DHAVE_CURSES_H" \ ./configure --prefix=/usr/local/mysql This will avoid problems with the `libstdc++' library and with C++ exceptions. If this doesn't help, you should compile a debug version and run it with a trace file or under `gdb'. *Note Using gdb on mysqld::. BSD Notes --------- FreeBSD Notes ............. FreeBSD 3.x is recommended for running *MySQL* since the thread package is much more integrated. The easiest and therefor the preferred way to install is to use the mysql-server and mysql-client ports available on `http://www.freebsd.org'. Using these gives you: * A working *MySQL* with all optimizations known to work on your version of FreeBSD enabled. * Automatic configuration and build. * Startup scripts installed in /usr/local/etc/rc.d. * Ability to see which files that are installed with pkg_info -L. And to remove them all with pkg_delete if you no longer want *MySQL* on that machine. It is recommended you use MIT-pthreads on FreeBSD 2.x and native threads on Versions 3 and up. It is possible to run with native threads on some late 2.2.x versions but you may encounter problems shutting down `mysqld'. The *MYSQL* Makefiles require GNU make (`gmake') to work. If you want to compile *MYSQL* you need to install GNU make first. Be sure to have your name resolver setup correct. Otherwise you may experience resolver delays or failures when connecting to `mysqld'. Make sure that the `localhost' entry in the `/etc/hosts' file is correct (otherwise you will have problems connecting to the database). The `/etc/hosts' file should start with a line: 127.0.0.1 localhost localhost.your.domain If you notice that `configure' will use MIT-pthreads, you should read the MIT-pthreads notes. *Note MIT-pthreads::. If you get an error from `make install' that it can't find `/usr/include/pthreads', `configure' didn't detect that you need MIT-pthreads. This is fixed by executing these commands: shell> rm config.cache shell> ./configure --with-mit-threads FreeBSD is also known to have a very low default file handle limit. *Note Not enough file handles::. Uncomment the ulimit -n section in safe_mysqld or raise the limits for the `mysqld' user in /etc/login.conf (and rebuild it with cap_mkdb /etc/login.conf). Also be sure you set the appropriate class for this user in the password file if you are not using the default (use: chpass mysqld-user-name). *Note `safe_mysqld': safe_mysqld. If you get problems with the current date in *MySQL*, setting the `TZ' variable will probably help. *Note Environment variables::. To get a secure and stable system you should only use FreeBSD kernels that are marked `-STABLE'. NetBSD notes ............ To compile on NetBSD you need GNU `make'. Otherwise the compile will crash when `make' tries to run `lint' on C++ files. OpenBSD Notes ............. OpenBSD 2.5 Notes ................. On OpenBSD Version 2.5, you can compile *MySQL* with native threads with the following options: CFLAGS=-pthread CXXFLAGS=-pthread ./configure --with-mit-threads=no OpenBSD 2.8 Notes ................. Our users have reported that OpenBSD 2.8 has a threading bug which causes problems with *MySQL*. The OpenBSD Developers have fixed the problem, but as of January 25th, 2001, it's only available in the "-current" branch. The symptoms of this threading bug are: slow response, high load, high CPU usage, and crashes. BSD/OS Notes ............ BSD/OS Version 2.x Notes ........................ If you get the following error when compiling *MySQL*, your `ulimit' value for virtual memory is too low: item_func.h: In method `Item_func_ge::Item_func_ge(const Item_func_ge &)': item_func.h:28: virtual memory exhausted make[2]: *** [item_func.o] Error 1 Try using `ulimit -v 80000' and run `make' again. If this doesn't work and you are using `bash', try switching to `csh' or `sh'; some BSDI users have reported problems with `bash' and `ulimit'. If you are using `gcc', you may also use have to use the `--with-low-memory' flag for `configure' to be able to compile `sql_yacc.cc'. If you get problems with the current date in *MySQL*, setting the `TZ' variable will probably help. *Note Environment variables::. BSD/OS Version 3.x Notes ........................ Upgrade to BSD/OS Version 3.1. If that is not possible, install BSDIpatch M300-038. Use the following command when configuring *MySQL*: shell> env CXX=shlicc++ CC=shlicc2 \ ./configure \ --prefix=/usr/local/mysql \ --localstatedir=/var/mysql \ --without-perl \ --with-unix-socket-path=/var/mysql/mysql.sock The following is also known to work: shell> env CC=gcc CXX=gcc CXXFLAGS=-O3 \ ./configure \ --prefix=/usr/local/mysql \ --with-unix-socket-path=/var/mysql/mysql.sock You can change the directory locations if you wish, or just use the defaults by not specifying any locations. If you have problems with performance under heavy load, try using the `--skip-thread-priority' option to `mysqld'! This will run all threads with the same priority; on BSDI Version 3.1, this gives better performance (at least until BSDI fixes their thread scheduler). If you get the error `virtual memory exhausted' while compiling, you should try using `ulimit -v 80000' and run `make' again. If this doesn't work and you are using `bash', try switching to `csh' or `sh'; some BSDI users have reported problems with `bash' and `ulimit'. BSD/OS Version 4.x Notes ........................ BSDI Version 4.x has some thread-related bugs. If you want to use *MySQL* on this, you should install all thread-related patches. At least M400-023 should be installed. On some BSDI Version 4.x systems, you may get problems with shared libraries. The symptom is that you can't execute any client programs, for example, `mysqladmin'. In this case you need to reconfigure not to use shared libraries with the `--disable-shared' option to configure. Some customers have had problems on BSDI 4.0.1 that the `mysqld' binary after a while can't open tables. This is because some library/system related bug causes `mysqld' to change current directory without asking for this! The fix is to either upgrade to 3.23.34 or after running `configure' remove the line `#define HAVE_REALPATH' from `config.h' before running make. Note that the above means that you can't symbolic link a database directories to another database directory or symbolic link a table to another database on BSDI! (Making a symbolic link to another disk is ok). Mac OS X Notes -------------- Mac OS X Public Beta .................... *MySQL* should work without any problems on Mac OS X Public Beta (Darwin). You don't need the pthread patches for this OS! Mac OS X Server ............... Before trying to configure *MySQL* on Mac OS X server you must first install the pthread package from `http://www.prnet.de/RegEx/mysql.html'. Our binary for Mac OS X is compiled on Rhapsody 5.5 with the following configure line: CC=gcc CFLAGS="-O2 -fomit-frame-pointer" CXX=gcc CXXFLAGS="-O2 -fomit-frame-pointer" ./configure --prefix=/usr/local/mysql "--with-comment=Official MySQL binary" --with-extra-charsets=complex --disable-shared You might want to also add aliases to your shell's resource file to access `mysql' and `mysqladmin' from the command line: alias mysql '/usr/local/mysql/bin/mysql' alias mysqladmin '/usr/local/mysql/bin/mysqladmin' Other Unix Notes ---------------- HP-UX Notes for Binary Distributions .................................... Some of the binary distributions of *MySQL* for HP-UX is distributed as an HP depot file and as a tar file. To use the depot file you must be running at least HP-UX 10.x to have access to HP's software depot tools. The HP version of *MySQL* was compiled on an HP 9000/8xx server under HP-UX 10.20, and uses MIT-pthreads. It is known to work well under this configuration. *MySQL* Version 3.22.26 and newer can also be built with HP's native thread package. Other configurations that may work: * HP 9000/7xx running HP-UX 10.20+ * HP 9000/8xx running HP-UX 10.30 The following configurations almost definitely won't work: * HP 9000/7xx or 8xx running HP-UX 10.x where x < 2 * HP 9000/7xx or 8xx running HP-UX 9.x To install the distribution, use one of the commands below, where `/path/to/depot' is the full pathname of the depot file: * To install everything, including the server, client and development tools: shell> /usr/sbin/swinstall -s /path/to/depot mysql.full * To install only the server: shell> /usr/sbin/swinstall -s /path/to/depot mysql.server * To install only the client package: shell> /usr/sbin/swinstall -s /path/to/depot mysql.client * To install only the development tools: shell> /usr/sbin/swinstall -s /path/to/depot mysql.developer The depot places binaries and libraries in `/opt/mysql' and data in `/var/opt/mysql'. The depot also creates the appropriate entries in `/etc/init.d' and `/etc/rc2.d' to start the server automatically at boot time. Obviously, this entails being `root' to install. To install the HP-UX tar.gz distribution, you must have a copy of GNU `tar'. HP-UX Version 10.20 Notes ......................... There are a couple of small problems when compiling *MySQL* on HP-UX. We recommend that you use `gcc' instead of the HP-UX native compiler, because `gcc' produces better code! We recommend using gcc 2.95 on HP-UX. Don't use high optimization flags (like -O6) as this may not be safe on HP-UX. Note that MIT-pthreads can't be compiled with the HP-UX compiler because it can't compile `.S' (assembler) files. The following configure line should work: CFLAGS="-DHPUX -I/opt/dce/include" CXXFLAGS="-DHPUX -I/opt/dce/include -felide-constructors -fno-exceptions -fno-rtti" CXX=gcc ./configure --with-pthread --with-named-thread-libs='-ldce' --prefix=/usr/local/mysql --disable-shared If you are compiling `gcc' 2.95 yourself, you should NOT link it with the DCE libraries (`libdce.a' or `libcma.a') if you want to compile *MySQL* with MIT-pthreads. If you mix the DCE and MIT-pthreads packages you will get a `mysqld' to which you cannot connect. Remove the DCE libraries while you compile `gcc' 2.95! HP-UX Version 11.x Notes ........................ For HP-UX Version 11.x we recommend *MySQL* Version 3.23.15 or later. Because of some critical bugs in the standard HP-UX libraries, you should install the following patches before trying to run *MySQL* on HP-UX 11.0: PHKL_22840 Streams cumulative PHNE_22397 ARPA cumulative This will solve a problem that one gets `EWOULDBLOCK' from `recv()' and `EBADF' from `accept()' in threaded applications. If you are using `gcc' 2.95.1 on an unpatched HP-UX 11.x system, you will get the error: In file included from /usr/include/unistd.h:11, from ../include/global.h:125, from mysql_priv.h:15, from item.cc:19: /usr/include/sys/unistd.h:184: declaration of C function ... /usr/include/sys/pthread.h:440: previous declaration ... In file included from item.h:306, from mysql_priv.h:158, from item.cc:19: The problem is that HP-UX doesn't define `pthreads_atfork()' consistently. It has conflicting prototypes in `/usr/include/sys/unistd.h':184 and `/usr/include/sys/pthread.h':440 (details below). One solution is to copy `/usr/include/sys/unistd.h' into `mysql/include' and edit `unistd.h' and change it to match the definition in `pthread.h'. Here's the diff: 183,184c183,184 < extern int pthread_atfork(void (*prepare)(), void (*parent)(), < void (*child)()); --- > extern int pthread_atfork(void (*prepare)(void), void (*parent)(void), > void (*child)(void)); After this, the following configure line should work: CFLAGS="-fomit-frame-pointer -O3 -fpic" CXX=gcc CXXFLAGS="-felide-constructors -fno-exceptions -fno-rtti -O3" ./configure --prefix=/usr/local/mysql --disable-shared Here is some information that a HP-UX Version 11.x user sent us about compiling *MySQL* with HP-UX:x compiler: Environment: proper compilers. setenv CC cc setenv CXX aCC flags setenv CFLAGS -D_REENTRANT setenv CXXFLAGS -D_REENTRANT setenv CPPFLAGS -D_REENTRANT % aCC -V aCC: HP ANSI C++ B3910B X.03.14.06 % cc -V /tmp/empty.c cpp.ansi: HP92453-01 A.11.02.00 HP C Preprocessor (ANSI) ccom: HP92453-01 A.11.01.00 HP C Compiler cc: "/tmp/empty.c", line 1: warning 501: Empty source file. configuration: ./configure --with-pthread \ --prefix=/source-control/mysql \ --with-named-thread-libs=-lpthread \ --with-low-memory added '#define _CTYPE_INCLUDED' to include/m_ctype.h. This symbol is the one defined in HP's /usr/include/ctype.h: /* Don't include std ctype.h when this is included */ #define _CTYPE_H #define __CTYPE_INCLUDED #define _CTYPE_INCLUDED #define _CTYPE_USING /* Don't put names in global namespace. */ * I had to use the compile-time flag `-D_REENTRANT' to get the compiler to recognize the prototype for `localtime_r'. Alternatively I could have supplied the prototype for `localtime_r'. But I wanted to catch other bugs without needing to run into them. I wasn't sure where I needed it, so I added it to all flags. * The optimization flags used by *MySQL* (-O3) are not recognized by HP's compilers. I did not change the flags. If you get the following error from `configure' checking for cc option to accept ANSI C... no configure: error: MySQL requires a ANSI C compiler (and a C++ compiler). Try gcc. See the Installation chapter in the Reference Manual. Check that you don't have the path to the K&R compiler before the path to the HP-UX C and C++ compiler. IBM-AIX notes ............. Automatic detection of `xlC' is missing from Autoconf, so a `configure' command something like this is needed when compiling *MySQL* (This example uses the IBM compiler): export CC="xlc_r -ma -O3 -qstrict -qoptimize=3 -qmaxmem=8192 " export CXX="xlC_r -ma -O3 -qstrict -qoptimize=3 -qmaxmem=8192" export CFLAGS="-I /usr/local/include" export LDLFAGS="-L /usr/local/lib" export CPPFLAGS=$CFLAGS export CXXFLAGS=$CFLAGS ./configure --prefix=/usr/local \ --localstatedir=/var/mysql \ --sysconfdir=/etc/mysql \ --sbindir='/usr/local/bin' \ --libexecdir='/usr/local/bin' \ --enable-thread-safe-client \ --enable-large-files Above are the options used to compile the *MySQL* distribution that can be found at `http://www-frec.bull.com/'. If you change the `-O3' to `-O2' in the above configure line, you must also remove the `-qstrict' option (this is a limitation in the IBM C compiler). If you are using `gcc' or `egcs' to compile *MySQL*, you *MUST* use the `-fno-exceptions' flag, as the exception handling in `gcc'/`egcs' is not thread safe! (This is tested with `egcs' 1.1.). There are also some known problems with IBM's assembler, which may cause it to generate bad code when used with gcc. We recommend the following `configure' line with `egcs' and `gcc 2.95' on AIX: CC="gcc -pipe -mcpu=power -Wa,-many" \ CXX="gcc -pipe -mcpu=power -Wa,-many" \ CXXFLAGS="-felide-constructors -fno-exceptions -fno-rtti" \ ./configure --prefix=/usr/local/mysql --with-low-memory The `-Wa,-many' is necessary for the compile to be successful. IBM is aware of this problem but is in to hurry to fix it because of the workaround available. We don't know if the `-fno-exceptions' is required with `gcc 2.95', but as *MySQL* doesn't use exceptions and the above option generates faster code, we recommend that you should always use this option with `egcs / gcc'. If you get a problem with assembler code try changing the -mcpu=xxx to match your cpu. Typically power2, power, or powerpc may need to be used, alternatively you might need to use 604 or 604e. I'm not positive but I would think using "power" would likely be safe most of the time, even on a power2 machine. If you don't know what your cpu is then do a "uname -m", this will give you back a string that looks like "000514676700", with a format of xxyyyyyymmss where xx and ss are always 0's, yyyyyy is a unique system id and mm is the id of the CPU Planar. A chart of these values can be found at `http://www.rs6000.ibm.com/doc_link/en_US/a_doc_lib/cmds/aixcmds5/uname.htm'. This will give you a machine type and a machine model you can use to determine what type of cpu you have. If you have problems with signals (*MySQL* dies unexpectedly under high load) you may have found an OS bug with threads and signals. In this case you can tell *MySQL* not to use signals by configuring with: shell> CFLAGS=-DDONT_USE_THR_ALARM CXX=gcc \ CXXFLAGS="-felide-constructors -fno-exceptions -fno-rtti -DDONT_USE_THR_ALARM" \ ./configure --prefix=/usr/local/mysql --with-debug --with-low-memory This doesn't affect the performance of *MySQL*, but has the side effect that you can't kill clients that are "sleeping" on a connection with `mysqladmin kill' or `mysqladmin shutdown'. Instead, the client will die when it issues its next command. On some versions of AIX, linking with `libbind.a' makes `getservbyname' core dump. This is an AIX bug and should be reported to IBM. For AIX 4.2.1 and gcc you have to do the following changes. After configuring, edit `config.h' and `include/my_config.h' and change the line that says #define HAVE_SNPRINTF 1 to #undef HAVE_SNPRINTF And finally, in `mysqld.cc' you need to add a prototype for initgoups. #ifdef _AIX41 extern "C" int initgroups(const char *,int); #endif SunOS 4 Notes ............. On SunOS 4, MIT-pthreads is needed to compile *MySQL*, which in turn means you will need GNU `make'. Some SunOS 4 systems have problems with dynamic libraries and `libtool'. You can use the following `configure' line to avoid this problem: shell> ./configure --disable-shared --with-mysqld-ldflags=-all-static When compiling `readline', you may get warnings about duplicate defines. These may be ignored. When compiling `mysqld', there will be some `implicit declaration of function' warnings. These may be ignored. Alpha-DEC-UNIX Notes (Tru64) ............................ If you are using egcs 1.1.2 on Digital Unix, you should upgrade to gcc 2.95.2, as egcs on DEC has some serious bugs! When compiling threaded programs under Digital Unix, the documentation recommends using the `-pthread' option for `cc' and `cxx' and the libraries `-lmach -lexc' (in addition to `-lpthread'). You should run `configure' something like this: CC="cc -pthread" CXX="cxx -pthread -O" \ ./configure --with-named-thread-libs="-lpthread -lmach -lexc -lc" When compiling `mysqld', you may see a couple of warnings like this: mysqld.cc: In function void handle_connections()': mysqld.cc:626: passing long unsigned int *' as argument 3 of accept(int,sockadddr *, int *)' You can safely ignore these warnings. They occur because `configure' can detect only errors, not warnings. If you start the server directly from the command line, you may have problems with it dying when you log out. (When you log out, your outstanding processes receive a `SIGHUP' signal.) If so, try starting the server like this: shell> nohup mysqld [options] & `nohup' causes the command following it to ignore any `SIGHUP' signal sent from the terminal. Alternatively, start the server by running `safe_mysqld', which invokes `mysqld' using `nohup' for you. *Note `safe_mysqld': safe_mysqld. If you get a problem when compiling mysys/get_opt.c, just remove the line #define _NO_PROTO from the start of that file! If you are using Compac's CC compiler, the following configure line should work: CC="cc -pthread" CFLAGS="-O4 -ansi_alias -ansi_args -fast -inline speed -speculate all -arch host" CXX="cxx -pthread" CXXFLAGS="-O4 -ansi_alias -ansi_args -fast -inline speed -speculate all -arch host" export CC CFLAGS CXX CXXFLAGS ./configure \ --prefix=/usr/local/mysql \ --with-low-memory \ --enable-large-files \ --enable-shared=yes \ --with-named-thread-libs="-lpthread -lmach -lexc -lc" gnumake If you get a problem with libtool, when compiling with shared libraries as above, when linking `mysql', you should be able to get around this by issuing: cd mysql /bin/sh ../libtool --mode=link cxx -pthread -O3 -DDBUG_OFF \ -O4 -ansi_alias -ansi_args -fast -inline speed \ -speculate all \ -arch host -DUNDEF_HAVE_GETHOSTBYNAME_R \ -o mysql mysql.o readline.o sql_string.o completion_hash.o \ ../readline/libreadline.a -lcurses \ ../libmysql/.libs/libmysqlclient.so -lm cd .. gnumake gnumake install scripts/mysql_install_db Alpha-DEC-OSF1 Notes .................... If you have problems compiling and have DEC `CC' and `gcc' installed, try running `configure' like this: CC=cc CFLAGS=-O CXX=gcc CXXFLAGS=-O3 \ ./configure --prefix=/usr/local/mysql If you get problems with the `c_asm.h' file, you can create and use a 'dummy' `c_asm.h' file with: touch include/c_asm.h CC=gcc CFLAGS=-I./include \ CXX=gcc CXXFLAGS=-O3 \ ./configure --prefix=/usr/local/mysql Note that the following problems with the `ld' program can be fixed by downloading the latest DEC (Compaq) patch kit from: `http://ftp.support.compaq.com/public/unix/'. On OSF1 V4.0D and compiler "DEC C V5.6-071 on Digital Unix V4.0 (Rev. 878)" the compiler had some strange behavior (undefined `asm' symbols). `/bin/ld' also appears to be broken (problems with `_exit undefined' errors occuring while linking `mysqld'). On this system, we have managed to compile *MySQL* with the following `configure' line, after replacing `/bin/ld' with the version from OSF 4.0C: CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql With the Digital compiler "C++ V6.1-029", the following should work: CC=cc -pthread CFLAGS=-O4 -ansi_alias -ansi_args -fast -inline speed -speculate all -arch host CXX=cxx -pthread CXXFLAGS=-O4 -ansi_alias -ansi_args -fast -inline speed -speculate all -arch host -noexceptions -nortti export CC CFLAGS CXX CXXFLAGS ./configure --prefix=/usr/mysql/mysql --with-mysqld-ldflags=-all-static --disable-shared --with-named-thread-libs="-lmach -lexc -lc" In some versions of OSF1, the `alloca()' function is broken. Fix this by removing the line in `config.h' that defines `'HAVE_ALLOCA''. The `alloca()' function also may have an incorrect prototype in `/usr/include/alloca.h'. This warning resulting from this can be ignored. `configure' will use the following thread libraries automatically: `--with-named-thread-libs="-lpthread -lmach -lexc -lc"'. When using `gcc', you can also try running `configure' like this: shell> CFLAGS=-D_PTHREAD_USE_D4 CXX=gcc CXXFLAGS=-O3 ./configure .... If you have problems with signals (*MySQL* dies unexpectedly under high load), you may have found an OS bug with threads and signals. In this case you can tell *MySQL* not to use signals by configuring with: shell> CFLAGS=-DDONT_USE_THR_ALARM \ CXXFLAGS=-DDONT_USE_THR_ALARM \ ./configure ... This doesn't affect the performance of *MySQL*, but has the side effect that you can't kill clients that are "sleeping" on a connection with `mysqladmin kill' or `mysqladmin shutdown'. Instead, the client will die when it issues its next command. With `gcc' 2.95.2, you will probably run into the following compile error: sql_acl.cc:1456: Internal compiler error in `scan_region', at except.c:2566 Please submit a full bug report. To fix this you should change to the `sql' directory and do a "cut and paste" of the last `gcc' line, but change `-O3' to `-O0' (or add `-O0' immediately after `gcc' if you don't have any `-O' option on your compile line.) After this is done you can just change back to the top-level directly and run `make' again. SGI Irix Notes .............. If you are using Irix Version 6.5.3 or newer `mysqld' will only be able to create threads if you run it as a user with `CAP_SCHED_MGT' privileges (like `root') or give the `mysqld' server this privilege with the following shell command: shell> chcap "CAP_SCHED_MGT+epi" /opt/mysql/libexec/mysqld You may have to undefine some things in `config.h' after running `configure' and before compiling. In some Irix implementations, the `alloca()' function is broken. If the `mysqld' server dies on some `SELECT' statements, remove the lines from `config.h' that define `HAVE_ALLOC' and `HAVE_ALLOCA_H'. If `mysqladmin create' doesn't work, remove the line from `config.h' that defines `HAVE_READDIR_R'. You may have to remove the `HAVE_TERM_H' line as well. SGI recommends that you install all of the patches on this page as a set: http://support.sgi.com/surfzone/patches/patchset/6.2_indigo.rps.html At the very minimum, you should install the latest kernel rollup, the latest `rld' rollup, and the latest `libc' rollup. You definitely need all the POSIX patches on this page, for pthreads support: `http://support.sgi.com/surfzone/patches/patchset/6.2_posix.rps.html' If you get the something like the following error when compiling `mysql.cc': "/usr/include/curses.h", line 82: error(1084): invalid combination of type Type the following in the top-level directory of your *MySQL* source tree: shell> extra/replace bool curses_bool < /usr/include/curses.h > include/curses.h shell> make There have also been reports of scheduling problems. If only one thread is running, things go slow. Avoid this by starting another client. This may lead to a 2-to-10-fold increase in execution speed thereafter for the other thread. This is a poorly understood problem with Irix threads; you may have to improvise to find solutions until this can be fixed. If you are compiling with `gcc', you can use the following `configure' command: CC=gcc CXX=gcc CXXFLAGS=-O3 \ ./configure --prefix=/usr/local/mysql --with-thread-safe-client --with-named-thread-libs=-lpthread On Irix 6.5.11 with native Irix C and C++ compilers ver. 7.3.1.2, the following is reported to work CC=cc CXX=CC CFLAGS='-O3 -n32 -TARG:platform=IP22 -I/usr/local/include \ -L/usr/local/lib' CXXFLAGS='-O3 -n32 -TARG:platform=IP22 \ -I/usr/local/include -L/usr/local/lib' ./configure --prefix=/usr/local/mysql \ --with-berkeley-db --with-innodb \ --with-libwrap=/usr/local --with-named-curses-libs=/usr/local/lib/libncurses.a SCO Notes ......... The current port is tested only on a "sco3.2v5.0.4" and "sco3.2v5.0.5" system. There has also been a lot of progress on a port to "sco 3.2v4.2". For the moment the recommended compiler on OpenServer is gcc 2.95.2. With this you should be able to compile *MySQL* with just: CC=gcc CXX=gcc ./configure ... (options) 1. For OpenServer 5.0.X you need to use GDS in Skunkware 95 (95q4c). This is necessary because GNU `gcc' 2.7.2 in Skunkware 97 does not have GNU `as'. You can also use `egcs' 1.1.2 or newer `http://www.egcs.com/'. If you are using `egcs' 1.1.2 you have to execute the following command: shell> cp -p /usr/include/pthread/stdtypes.h /usr/local/lib/gcc-lib/i386-pc-sco3.2v5.0.5/egcs-2.91.66/include/pthread/ 2. You need the port of GCC 2.5.x for this product and the Development system. They are required on this version of SCO Unix. You cannot just use the GCC Dev system. 3. You should get the FSU Pthreads package and install it first. This can be found at `http://www.cs.wustl.edu/~schmidt/ACE_wrappers/FSU-threads.tar.gz'. You can also get a precompiled package from `http://www.mysql.com/Downloads/SCO/FSU-threads-3.5c.tar.gz'. 4. FSU Pthreads can be compiled with SCO Unix 4.2 with tcpip. Or OpenServer 3.0 or Open Desktop 3.0 (OS 3.0 ODT 3.0), with the SCO Development System installed using a good port of GCC 2.5.x ODT or OS 3.0 you will need a good port of GCC 2.5.x There are a lot of problems without a good port. The port for this product requires the SCO Unix Development system. Without it, you are missing the libraries and the linker that is needed. 5. To build FSU Pthreads on your system, do the following: a. Run `./configure' in the `threads/src' directory and select the SCO OpenServer option. This command copies `Makefile.SCO5' to `Makefile'. b. Run `make'. c. To install in the default `/usr/include' directory, login as root, then `cd' to the `thread/src' directory, and run `make install'. 6. Remember to use GNU `make' when making *MySQL*. 7. If you don't start `safe_mysqld' as root, you probably will get only the default 110 open files per process. `mysqld' will write a note about this in the log file. 8. With SCO 3.2V5.0.5, you should use FSU Pthreads version 3.5c or newer. You should also use gcc 2.95.2 or newer! The following `configure' command should work: shell> ./configure --prefix=/usr/local/mysql --disable-shared 9. With SCO 3.2V4.2, you should use FSU Pthreads version 3.5c or newer. The following `configure' command should work: shell> CFLAGS="-D_XOPEN_XPG4" CXX=gcc CXXFLAGS="-D_XOPEN_XPG4" \ ./configure \ --prefix=/usr/local/mysql \ --with-named-thread-libs="-lgthreads -lsocket -lgen -lgthreads" \ --with-named-curses-libs="-lcurses" You may get some problems with some include files. In this case, you can find new SCO-specific include files at `http://www.mysql.com/Downloads/SCO/SCO-3.2v4.2-includes.tar.gz'. You should unpack this file in the `include' directory of your *MySQL* source tree. SCO development notes: * *MySQL* should automatically detect FSU Pthreads and link `mysqld' with `-lgthreads -lsocket -lgthreads'. * The SCO development libraries are re-entrant in FSU Pthreads. SCO claims that its libraries' functions are re-entrant, so they must be reentrant with FSU Pthreads. FSU Pthreads on OpenServer tries to use the SCO scheme to make re-entrant libraries. * FSU Pthreads (at least the version at `http://www.mysql.com/') comes linked with GNU `malloc'. If you encounter problems with memory usage, make sure that `gmalloc.o' is included in `libgthreads.a' and `libgthreads.so'. * In FSU Pthreads, the following system calls are pthreads-aware: `read()', `write()', `getmsg()', `connect()', `accept()', `select()', and `wait()'. If you want to install DBI on SCO, you have to edit the `Makefile' in DBI-xxx and each subdirectory. Note that the following assumes gcc 2.95.2 or newer: OLD: NEW: CC = cc CC = gcc CCCDLFLAGS = -KPIC -W1,-Bexport CCCDLFLAGS = -fpic CCDLFLAGS = -wl,-Bexport CCDLFLAGS = LD = ld LD = gcc -G -fpic LDDLFLAGS = -G -L/usr/local/lib LDDLFLAGS = -L/usr/local/lib LDFLAGS = -belf -L/usr/local/lib LDFLAGS = -L/usr/local/lib LD = ld LD = gcc -G -fpic OPTIMISE = -Od OPTIMISE = -O1 OLD: CCCFLAGS = -belf -dy -w0 -U M_XENIX -DPERL_SCO5 -I/usr/local/include NEW: CCFLAGS = -U M_XENIX -DPERL_SCO5 -I/usr/local/include This is because the Perl dynaloader will not load the `DBI' modules if they were compiled with `icc' or `cc'. Perl works best when compiled with `cc'. SCO Unixware Version 7.0 Notes .............................. You must use a version of *MySQL* at least as recent as Version 3.22.13 because that version fixes some portability problems under Unixware. We have been able to compile *MySQL* with the following `configure' command on Unixware Version 7.0.1: CC=cc CXX=CC ./configure --prefix=/usr/local/mysql If you want to use `gcc', you must use `gcc' 2.95.2 or newer. OS/2 Notes ---------- *MySQL* uses quite a few open files. Because of this, you should add something like the following to your `CONFIG.SYS' file: SET EMXOPT=-c -n -h1024 If you don't do this, you will probably run into the following error: File 'xxxx' not found (Errcode: 24) When using *MySQL* with OS/2 Warp 3, FixPack 29 or above is required. With OS/2 Warp 4, FixPack 4 or above is required. This is a requirement of the Pthreads library. *MySQL* must be installed in a partition that supports long filenames such as HPFS, FAT32, etc. The `INSTALL.CMD' script must be run from OS/2's own `CMD.EXE' and may not work with replacement shells such as `4OS2.EXE'. The `scripts/mysql-install-db' script has been renamed. It is now called `install.cmd' and is a REXX script, which will set up the default *MySQL* security settings and create the WorkPlace Shell icons for *MySQL*. Dynamic module support is compiled in but not fully tested. Dynamic modules should be compiled using the Pthreads run-time library. gcc -Zdll -Zmt -Zcrtdll=pthrdrtl -I../include -I../regex -I.. \ -o example udf_example.cc -L../lib -lmysqlclient udf_example.def mv example.dll example.udf *Note:* Due to limitations in OS/2, UDF module name stems must not exceed 8 characters. Modules are stored in the `/mysql2/udf' directory; the `safe-mysqld.cmd' script will put this directory in the `BEGINLIBPATH' environment variable. When using UDF modules, specified extensions are ignored -- it is assumed to be `.udf'. For example, in Unix, the shared module might be named `example.so' and you would load a function from it like this: mysql> CREATE FUNCTION metaphon RETURNS STRING SONAME "example.so"; Is OS/2, the module would be named `example.udf', but you would not specify the module extension: mysql> CREATE FUNCTION metaphon RETURNS STRING SONAME "example"; BeOS Notes ---------- We are really interested in getting *MySQL* to work on BeOS, but unfortunately we don't have any person who knows BeOS or has time to do a port. We are interested in finding someone to do a port, and we will help them with any technical questions they may have while doing the port. We have previously talked with some BeOS developers that have said that *MySQL* is 80% ported to BeOS, but we haven't heard from them in a while. Novell Netware Notes -------------------- We are really interested in getting *MySQL* to work on Netware, but unfortunately we don't have any person who knows Netware or has time to do a port. We are interested in finding someone to do a port, and we will help them with any technical questions they may have while doing the port. Introduction to MySQL: A MySQL Tutorial *************************************** This chapter provides a tutorial introduction to *MySQL* by showing how to use the `mysql' client program to create and use a simple database. `mysql' (sometimes referred to as the "terminal monitor" or just "monitor") is an interactive program that allows you to connect to a *MySQL* server, run queries, and view the results. `mysql' may also be used in batch mode: you place your queries in a file beforehand, then tell `mysql' to execute the contents of the file. Both ways of using `mysql' are covered here. To see a list of options provided by `mysql', invoke it with the `--help' option: shell> mysql --help This chapter assumes that `mysql' is installed on your machine and that a *MySQL* server is available to which you can connect. If this is not true, contact your *MySQL* administrator. (If _you_ are the administrator, you will need to consult other sections of this manual.) This chapter describes the entire process of setting up and using a database. If you are interested only in accessing an already-existing database, you may want to skip over the sections that describe how to create the database and the tables it contains. Because this chapter is tutorial in nature, many details are necessarily left out. Consult the relevant sections of the manual for more information on the topics covered here. Connecting to and Disconnecting from the Server =============================================== To connect to the server, you'll usually need to provide a *MySQL* user name when you invoke `mysql' and, most likely, a password. If the server runs on a machine other than the one where you log in, you'll also need to specify a hostname. Contact your administrator to find out what connection parameters you should use to connect (that is, what host, user name, and password to use). Once you know the proper parameters, you should be able to connect like this: shell> mysql -h host -u user -p Enter password: ******** The `********' represents your password; enter it when `mysql' displays the `Enter password:' prompt. If that works, you should see some introductory information followed by a `mysql>' prompt: shell> mysql -h host -u user -p Enter password: ******** Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 459 to server version: 3.22.20a-log Type 'help' for help. mysql> The prompt tells you that `mysql' is ready for you to enter commands. Some *MySQL* installations allow users to connect as the anonymous (unnamed) user to the server running on the local host. If this is the case on your machine, you should be able to connect to that server by invoking `mysql' without any options: shell> mysql After you have connected successfully, you can disconnect any time by typing `QUIT' at the `mysql>' prompt: mysql> QUIT Bye You can also disconnect by pressing Control-D. Most examples in the following sections assume you are connected to the server. They indicate this by the `mysql>' prompt. Entering Queries ================ Make sure you are connected to the server, as discussed in the previous section. Doing so will not in itself select any database to work with, but that's okay. At this point, it's more important to find out a little about how to issue queries than to jump right in creating tables, loading data into them, and retrieving data from them. This section describes the basic principles of entering commands, using several queries you can try out to familiarize yourself with how `mysql' works. Here's a simple command that asks the server to tell you its version number and the current date. Type it in as shown below following the `mysql>' prompt and hit the RETURN key: mysql> SELECT VERSION(), CURRENT_DATE; +--------------+--------------+ | version() | CURRENT_DATE | +--------------+--------------+ | 3.22.20a-log | 1999-03-19 | +--------------+--------------+ 1 row in set (0.01 sec) mysql> This query illustrates several things about `mysql': * A command normally consists of a SQL statement followed by a semicolon. (There are some exceptions where a semicolon is not needed. `QUIT', mentioned earlier, is one of them. We'll get to others later.) * When you issue a command, `mysql' sends it to the server for execution and displays the results, then prints another `mysql>' to indicate that it is ready for another command. * `mysql' displays query output as a table (rows and columns). The first row contains labels for the columns. The rows following are the query results. Normally, column labels are the names of the columns you fetch from database tables. If you're retrieving the value of an expression rather than a table column (as in the example just shown), `mysql' labels the column using the expression itself. * `mysql' shows how many rows were returned and how long the query took to execute, which gives you a rough idea of server performance. These values are imprecise because they represent wall clock time (not CPU or machine time), and because they are affected by factors such as server load and network latency. (For brevity, the "rows in set" line is not shown in the remaining examples in this chapter.) Keywords may be entered in any lettercase. The following queries are equivalent: mysql> SELECT VERSION(), CURRENT_DATE; mysql> select version(), current_date; mysql> SeLeCt vErSiOn(), current_DATE; Here's another query. It demonstrates that you can use `mysql' as a simple calculator: mysql> SELECT SIN(PI()/4), (4+1)*5; +-------------+---------+ | SIN(PI()/4) | (4+1)*5 | +-------------+---------+ | 0.707107 | 25 | +-------------+---------+ The commands shown thus far have been relatively short, single-line statements. You can even enter multiple statements on a single line. Just end each one with a semicolon: mysql> SELECT VERSION(); SELECT NOW(); +--------------+ | version() | +--------------+ | 3.22.20a-log | +--------------+ +---------------------+ | NOW() | +---------------------+ | 1999-03-19 00:15:33 | +---------------------+ A command need not be given all on a single line, so lengthy commands that require several lines are not a problem. `mysql' determines where your statement ends by looking for the terminating semicolon, not by looking for the end of the input line. (In other words, `mysql' accepts free-format input: it collects input lines but does not execute them until it sees the semicolon.) Here's a simple multiple-line statement: mysql> SELECT -> USER() -> , -> CURRENT_DATE; +--------------------+--------------+ | USER() | CURRENT_DATE | +--------------------+--------------+ | joesmith@localhost | 1999-03-18 | +--------------------+--------------+ In this example, notice how the prompt changes from `mysql>' to `->' after you enter the first line of a multiple-line query. This is how `mysql' indicates that it hasn't seen a complete statement and is waiting for the rest. The prompt is your friend, because it provides valuable feedback. If you use that feedback, you will always be aware of what `mysql' is waiting for. If you decide you don't want to execute a command that you are in the process of entering, cancel it by typing `\c': mysql> SELECT -> USER() -> \c mysql> Here, too, notice the prompt. It switches back to `mysql>' after you type `\c', providing feedback to indicate that `mysql' is ready for a new command. The following table shows each of the prompts you may see and summarizes what they mean about the state that `mysql' is in: *Prompt**Meaning* `mysql>'Ready for new command. ` Waiting for next line of multiple-line command. ->' ` Waiting for next line, collecting a string that begins with a '>' single quote (`''). ` Waiting for next line, collecting a string that begins with a ">' double quote (`"'). Multiple-line statements commonly occur by accident when you intend to issue a command on a single line, but forget the terminating semicolon. In this case, `mysql' waits for more input: mysql> SELECT USER() -> If this happens to you (you think you've entered a statement but the only response is a `->' prompt), most likely `mysql' is waiting for the semicolon. If you don't notice what the prompt is telling you, you might sit there for a while before realizing what you need to do. Enter a semicolon to complete the statement, and `mysql' will execute it: mysql> SELECT USER() -> ; +--------------------+ | USER() | +--------------------+ | joesmith@localhost | +--------------------+ The `'>' and `">' prompts occur during string collection. In *MySQL*, you can write strings surrounded by either `'' or `"' characters (for example, `'hello'' or `"goodbye"'), and `mysql' lets you enter strings that span multiple lines. When you see a `'>' or `">' prompt, it means that you've entered a line containing a string that begins with a `'' or `"' quote character, but have not yet entered the matching quote that terminates the string. That's fine if you really are entering a multiple-line string, but how likely is that? Not very. More often, the `'>' and `">' prompts indicate that you've inadvertantly left out a quote character. For example: mysql> SELECT * FROM my_table WHERE name = "Smith AND age < 30; "> If you enter this `SELECT' statement, then hit RETURN and wait for the result, nothing will happen. Instead of wondering why this query takes so long, notice the clue provided by the `">' prompt. It tells you that `mysql' expects to see the rest of an unterminated string. (Do you see the error in the statement? The string `"Smith' is missing the second quote.) At this point, what do you do? The simplest thing is to cancel the command. However, you cannot just type `\c' in this case, because `mysql' interprets it as part of the string that it is collecting! Instead, enter the closing quote character (so `mysql' knows you've finished the string), then type `\c': mysql> SELECT * FROM my_table WHERE name = "Smith AND age < 30; "> "\c mysql> The prompt changes back to `mysql>', indicating that `mysql' is ready for a new command. It's important to know what the `'>' and `">' prompts signify, because if you mistakenly enter an unterminated string, any further lines you type will appear to be ignored by `mysql' -- including a line containing `QUIT'! This can be quite confusing, especially if you don't know that you need to supply the terminating quote before you can cancel the current command. Creating and Using a Database ============================= Now that you know how to enter commands, it's time to access a database. Suppose you have several pets in your home (your menagerie) and you'd like to keep track of various types of information about them. You can do so by creating tables to hold your data and loading them with the desired information. Then you can answer different sorts of questions about your animals by retrieving data from the tables. This section shows you how to: * Create a database * Create a table * Load data into the table * Retrieve data from the table in various ways * Use multiple tables The menagerie database will be simple (deliberately), but it is not difficult to think of real-world situations in which a similar type of database might be used. For example, a database like this could be used by a farmer to keep track of livestock, or by a veterinarian to keep track of patient records. A menagerie distribution containing some of the queries and sample data used in the following sections can be obtained from the *MySQL* Web site. It's available in either compressed `tar' format (http://www.mysql.com/Downloads/Contrib/Examples/menagerie.tar.gz) or Zip format (http://www.mysql.com/Downloads/Contrib/Examples/menagerie.zip). Use the `SHOW' statement to find out what databases currently exist on the server: mysql> SHOW DATABASES; +----------+ | Database | +----------+ | mysql | | test | | tmp | +----------+ The list of databases is probably different on your machine, but the `mysql' and `test' databases are likely to be among them. The `mysql' database is required because it describes user access privileges. The `test' database is often provided as a workspace for users to try things out. If the `test' database exists, try to access it: mysql> USE test Database changed Note that `USE', like `QUIT', does not require a semicolon. (You can terminate such statements with a semicolon if you like; it does no harm.) The `USE' statement is special in another way, too: it must be given on a single line. You can use the `test' database (if you have access to it) for the examples that follow, but anything you create in that database can be removed by anyone else with access to it. For this reason, you should probably ask your *MySQL* administrator for permission to use a database of your own. Suppose you want to call yours `menagerie'. The administrator needs to execute a command like this: mysql> GRANT ALL ON menagerie.* TO your_mysql_name; where `your_mysql_name' is the *MySQL* user name assigned to you. Creating and Selecting a Database --------------------------------- If the administrator creates your database for you when setting up your permissions, you can begin using it. Otherwise, you need to create it yourself: mysql> CREATE DATABASE menagerie; Under Unix, database names are case sensitive (unlike SQL keywords), so you must always refer to your database as `menagerie', not as `Menagerie', `MENAGERIE', or some other variant. This is also true for table names. (Under Windows, this restriction does not apply, although you must refer to databases and tables using the same lettercase throughout a given query.) Creating a database does not select it for use; you must do that explicitly. To make `menagerie' the current database, use this command: mysql> USE menagerie Database changed Your database needs to be created only once, but you must select it for use each time you begin a `mysql' session. You can do this by issuing a `USE' statement as shown above. Alternatively, you can select the database on the command line when you invoke `mysql'. Just specify its name after any connection parameters that you might need to provide. For example: shell> mysql -h host -u user -p menagerie Enter password: ******** Note that `menagerie' is not your password on the command just shown. If you want to supply your password on the command line after the `-p' option, you must do so with no intervening space (for example, as `-pmypassword', not as `-p mypassword'). However, putting your password on the command line is not recommended, because doing so exposes it to snooping by other users logged in on your machine. Creating a Table ---------------- Creating the database is the easy part, but at this point it's empty, as `SHOW TABLES' will tell you: mysql> SHOW TABLES; Empty set (0.00 sec) The harder part is deciding what the structure of your database should be: what tables you will need and what columns will be in each of them. You'll want a table that contains a record for each of your pets. This can be called the `pet' table, and it should contain, as a bare minimum, each animal's name. Because the name by itself is not very interesting, the table should contain other information. For example, if more than one person in your family keeps pets, you might want to list each animal's owner. You might also want to record some basic descriptive information such as species and sex. How about age? That might be of interest, but it's not a good thing to store in a database. Age changes as time passes, which means you'd have to update your records often. Instead, it's better to store a fixed value such as date of birth. Then, whenever you need age, you can calculate it as the difference between the current date and the birth date. *MySQL* provides functions for doing date arithmetic, so this is not difficult. Storing birth date rather than age has other advantages, too: * You can use the database for tasks such as generating reminders for upcoming pet birthdays. (If you think this type of query is somewhat silly, note that it is the same question you might ask in the context of a business database to identify clients to whom you'll soon need to send out birthday greetings, for that computer-assisted personal touch.) * You can calculate age in relation to dates other than the current date. For example, if you store death date in the database, you can easily calculate how old a pet was when it died. You can probably think of other types of information that would be useful in the `pet' table, but the ones identified so far are sufficient for now: name, owner, species, sex, birth, and death. Use a `CREATE TABLE' statement to specify the layout of your table: mysql> CREATE TABLE pet (name VARCHAR(20), owner VARCHAR(20), -> species VARCHAR(20), sex CHAR(1), birth DATE, death DATE); `VARCHAR' is a good choice for the `name', `owner', and `species' columns because the column values will vary in length. The lengths of those columns need not all be the same, and need not be `20'. You can pick any length from `1' to `255', whatever seems most reasonable to you. (If you make a poor choice and it turns out later that you need a longer field, *MySQL* provides an `ALTER TABLE' statement.) Animal sex can be represented in a variety of ways, for example, `"m"' and `"f"', or perhaps `"male"' and `"female"'. It's simplest to use the single characters `"m"' and `"f"'. The use of the `DATE' data type for the `birth' and `death' columns is a fairly obvious choice. Now that you have created a table, `SHOW TABLES' should produce some output: mysql> SHOW TABLES; +---------------------+ | Tables in menagerie | +---------------------+ | pet | +---------------------+ To verify that your table was created the way you expected, use a `DESCRIBE' statement: mysql> DESCRIBE pet; +---------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +---------+-------------+------+-----+---------+-------+ | name | varchar(20) | YES | | NULL | | | owner | varchar(20) | YES | | NULL | | | species | varchar(20) | YES | | NULL | | | sex | char(1) | YES | | NULL | | | birth | date | YES | | NULL | | | death | date | YES | | NULL | | +---------+-------------+------+-----+---------+-------+ You can use `DESCRIBE' any time, for example, if you forget the names of the columns in your table or what types they are. Loading Data into a Table ------------------------- After creating your table, you need to populate it. The `LOAD DATA' and `INSERT' statements are useful for this. Suppose your pet records can be described as shown below. (Observe that *MySQL* expects dates in `YYYY-MM-DD' format; this may be different than what you are used to.) *name* *owner* *species* *sex* *birth* *death* Fluffy Harold cat f 1993-02-04 Claws Gwen cat m 1994-03-17 Buffy Harold dog f 1989-05-13 Fang Benny dog m 1990-08-27 Bowser Diane dog m 1989-08-31 1995-07-29 Chirpy Gwen bird f 1998-09-11 Whistler Gwen bird 1997-12-09 Slim Benny snake m 1996-04-29 Because you are beginning with an empty table, an easy way to populate it is to create a text file containing a row for each of your animals, then load the contents of the file into the table with a single statement. You could create a text file `pet.txt' containing one record per line, with values separated by tabs, and given in the order in which the columns were listed in the `CREATE TABLE' statement. For missing values (such as unknown sexes or death dates for animals that are still living), you can use `NULL' values. To represent these in your text file, use `\N'. For example, the record for Whistler the bird would look like this (where the whitespace between values is a single tab character): `Whistler' `Gwen' `bird' `\N' `1997-12-09' `\N' To load the text file `pet.txt' into the `pet' table, use this command: mysql> LOAD DATA LOCAL INFILE "pet.txt" INTO TABLE pet; You can specify the column value separator and end of line marker explicitly in the `LOAD DATA' statement if you wish, but the defaults are tab and linefeed. These are sufficient for the statement to read the file `pet.txt' properly. When you want to add new records one at a time, the `INSERT' statement is useful. In its simplest form, you supply values for each column, in the order in which the columns were listed in the `CREATE TABLE' statement. Suppose Diane gets a new hamster named Puffball. You could add a new record using an `INSERT' statement like this: mysql> INSERT INTO pet -> VALUES ('Puffball','Diane','hamster','f','1999-03-30',NULL); Note that string and date values are specified as quoted strings here. Also, with `INSERT', you can insert `NULL' directly to represent a missing value. You do not use `\N' like you do with `LOAD DATA'. From this example, you should be able to see that there would be a lot more typing involved to load your records initially using several `INSERT' statements rather than a single `LOAD DATA' statement. Retrieving Information from a Table ----------------------------------- The `SELECT' statement is used to pull information from a table. The general form of the statement is: SELECT what_to_select FROM which_table WHERE conditions_to_satisfy `what_to_select' indicates what you want to see. This can be a list of columns, or `*' to indicate "all columns." `which_table' indicates the table from which you want to retrieve data. The `WHERE' clause is optional. If it's present, `conditions_to_satisfy' specifies conditions that rows must satisfy to qualify for retrieval. Selecting All Data .................. The simplest form of `SELECT' retrieves everything from a table: mysql> SELECT * FROM pet; +----------+--------+---------+------+------------+------------+ | name | owner | species | sex | birth | death | +----------+--------+---------+------+------------+------------+ | Fluffy | Harold | cat | f | 1993-02-04 | NULL | | Claws | Gwen | cat | m | 1994-03-17 | NULL | | Buffy | Harold | dog | f | 1989-05-13 | NULL | | Fang | Benny | dog | m | 1990-08-27 | NULL | | Bowser | Diane | dog | m | 1998-08-31 | 1995-07-29 | | Chirpy | Gwen | bird | f | 1998-09-11 | NULL | | Whistler | Gwen | bird | NULL | 1997-12-09 | NULL | | Slim | Benny | snake | m | 1996-04-29 | NULL | | Puffball | Diane | hamster | f | 1999-03-30 | NULL | +----------+--------+---------+------+------------+------------+ This form of `SELECT' is useful if you want to review your entire table, for instance, after you've just loaded it with your initial dataset. As it happens, the output just shown reveals an error in your data file: Bowser appears to have been born after he died! Consulting your original pedigree papers, you find that the correct birth year is 1989, not 1998. There are are least a couple of ways to fix this: * Edit the file `pet.txt' to correct the error, then empty the table and reload it using `DELETE' and `LOAD DATA': mysql> SET AUTOCOMMIT=1; # Used for quick re-create of the table mysql> DELETE FROM pet; mysql> LOAD DATA LOCAL INFILE "pet.txt" INTO TABLE pet; However, if you do this, you must also re-enter the record for Puffball. * Fix only the erroneous record with an `UPDATE' statement: mysql> UPDATE pet SET birth = "1989-08-31" WHERE name = "Bowser"; As shown above, it is easy to retrieve an entire table. But typically you don't want to do that, particularly when the table becomes large. Instead, you're usually more interested in answering a particular question, in which case you specify some constraints on the information you want. Let's look at some selection queries in terms of questions about your pets that they answer. Selecting Particular Rows ......................... You can select only particular rows from your table. For example, if you want to verify the change that you made to Bowser's birth date, select Bowser's record like this: mysql> SELECT * FROM pet WHERE name = "Bowser"; +--------+-------+---------+------+------------+------------+ | name | owner | species | sex | birth | death | +--------+-------+---------+------+------------+------------+ | Bowser | Diane | dog | m | 1989-08-31 | 1995-07-29 | +--------+-------+---------+------+------------+------------+ The output confirms that the year is correctly recorded now as 1989, not 1998. String comparisons are normally case insensitive, so you can specify the name as `"bowser"', `"BOWSER"', etc. The query result will be the same. You can specify conditions on any column, not just `name'. For example, if you want to know which animals were born after 1998, test the `birth' column: mysql> SELECT * FROM pet WHERE birth >= "1998-1-1"; +----------+-------+---------+------+------------+-------+ | name | owner | species | sex | birth | death | +----------+-------+---------+------+------------+-------+ | Chirpy | Gwen | bird | f | 1998-09-11 | NULL | | Puffball | Diane | hamster | f | 1999-03-30 | NULL | +----------+-------+---------+------+------------+-------+ You can combine conditions, for example, to locate female dogs: mysql> SELECT * FROM pet WHERE species = "dog" AND sex = "f"; +-------+--------+---------+------+------------+-------+ | name | owner | species | sex | birth | death | +-------+--------+---------+------+------------+-------+ | Buffy | Harold | dog | f | 1989-05-13 | NULL | +-------+--------+---------+------+------------+-------+ The preceding query uses the `AND' logical operator. There is also an `OR' operator: mysql> SELECT * FROM pet WHERE species = "snake" OR species = "bird"; +----------+-------+---------+------+------------+-------+ | name | owner | species | sex | birth | death | +----------+-------+---------+------+------------+-------+ | Chirpy | Gwen | bird | f | 1998-09-11 | NULL | | Whistler | Gwen | bird | NULL | 1997-12-09 | NULL | | Slim | Benny | snake | m | 1996-04-29 | NULL | +----------+-------+---------+------+------------+-------+ `AND' and `OR' may be intermixed. If you do that, it's a good idea to use parentheses to indicate how conditions should be grouped: mysql> SELECT * FROM pet WHERE (species = "cat" AND sex = "m") -> OR (species = "dog" AND sex = "f"); +-------+--------+---------+------+------------+-------+ | name | owner | species | sex | birth | death | +-------+--------+---------+------+------------+-------+ | Claws | Gwen | cat | m | 1994-03-17 | NULL | | Buffy | Harold | dog | f | 1989-05-13 | NULL | +-------+--------+---------+------+------------+-------+ Selecting Particular Columns ............................ If you don't want to see entire rows from your table, just name the columns in which you're interested, separated by commas. For example, if you want to know when your animals were born, select the `name' and `birth' columns: mysql> SELECT name, birth FROM pet; +----------+------------+ | name | birth | +----------+------------+ | Fluffy | 1993-02-04 | | Claws | 1994-03-17 | | Buffy | 1989-05-13 | | Fang | 1990-08-27 | | Bowser | 1989-08-31 | | Chirpy | 1998-09-11 | | Whistler | 1997-12-09 | | Slim | 1996-04-29 | | Puffball | 1999-03-30 | +----------+------------+ To find out who owns pets, use this query: mysql> SELECT owner FROM pet; +--------+ | owner | +--------+ | Harold | | Gwen | | Harold | | Benny | | Diane | | Gwen | | Gwen | | Benny | | Diane | +--------+ However, notice that the query simply retrieves the `owner' field from each record, and some of them appear more than once. To minimize the output, retrieve each unique output record just once by adding the keyword `DISTINCT': mysql> SELECT DISTINCT owner FROM pet; +--------+ | owner | +--------+ | Benny | | Diane | | Gwen | | Harold | +--------+ You can use a `WHERE' clause to combine row selection with column selection. For example, to get birth dates for dogs and cats only, use this query: mysql> SELECT name, species, birth FROM pet -> WHERE species = "dog" OR species = "cat"; +--------+---------+------------+ | name | species | birth | +--------+---------+------------+ | Fluffy | cat | 1993-02-04 | | Claws | cat | 1994-03-17 | | Buffy | dog | 1989-05-13 | | Fang | dog | 1990-08-27 | | Bowser | dog | 1989-08-31 | +--------+---------+------------+ Sorting Rows ............ You may have noticed in the preceding examples that the result rows are displayed in no particular order. However, it's often easier to examine query output when the rows are sorted in some meaningful way. To sort a result, use an `ORDER BY' clause. Here are animal birthdays, sorted by date: mysql> SELECT name, birth FROM pet ORDER BY birth; +----------+------------+ | name | birth | +----------+------------+ | Buffy | 1989-05-13 | | Bowser | 1989-08-31 | | Fang | 1990-08-27 | | Fluffy | 1993-02-04 | | Claws | 1994-03-17 | | Slim | 1996-04-29 | | Whistler | 1997-12-09 | | Chirpy | 1998-09-11 | | Puffball | 1999-03-30 | +----------+------------+ To sort in reverse order, add the `DESC' (descending) keyword to the name of the column you are sorting by: mysql> SELECT name, birth FROM pet ORDER BY birth DESC; +----------+------------+ | name | birth | +----------+------------+ | Puffball | 1999-03-30 | | Chirpy | 1998-09-11 | | Whistler | 1997-12-09 | | Slim | 1996-04-29 | | Claws | 1994-03-17 | | Fluffy | 1993-02-04 | | Fang | 1990-08-27 | | Bowser | 1989-08-31 | | Buffy | 1989-05-13 | +----------+------------+ You can sort on multiple columns. For example, to sort by type of animal, then by birth date within animal type with youngest animals first, use the following query: mysql> SELECT name, species, birth FROM pet ORDER BY species, birth DESC; +----------+---------+------------+ | name | species | birth | +----------+---------+------------+ | Chirpy | bird | 1998-09-11 | | Whistler | bird | 1997-12-09 | | Claws | cat | 1994-03-17 | | Fluffy | cat | 1993-02-04 | | Fang | dog | 1990-08-27 | | Bowser | dog | 1989-08-31 | | Buffy | dog | 1989-05-13 | | Puffball | hamster | 1999-03-30 | | Slim | snake | 1996-04-29 | +----------+---------+------------+ Note that the `DESC' keyword applies only to the column name immediately preceding it (`birth'); `species' values are still sorted in ascending order. Date Calculations ................. *MySQL* provides several functions that you can use to perform calculations on dates, for example, to calculate ages or extract parts of dates. To determine how many years old each of your pets is, compute age as the difference between the birth date and the current date. Do this by converting the two dates to days, take the difference, and divide by 365 (the number of days in a year): mysql> SELECT name, (TO_DAYS(NOW())-TO_DAYS(birth))/365 FROM pet; +----------+-------------------------------------+ | name | (TO_DAYS(NOW())-TO_DAYS(birth))/365 | +----------+-------------------------------------+ | Fluffy | 6.15 | | Claws | 5.04 | | Buffy | 9.88 | | Fang | 8.59 | | Bowser | 9.58 | | Chirpy | 0.55 | | Whistler | 1.30 | | Slim | 2.92 | | Puffball | 0.00 | +----------+-------------------------------------+ Although the query works, there are some things about it that could be improved. First, the result could be scanned more easily if the rows were presented in some order. Second, the heading for the age column isn't very meaningful. The first problem can be handled by adding an `ORDER BY name' clause to sort the output by name. To deal with the column heading, provide a name for the column so that a different label appears in the output (this is called a column alias): mysql> SELECT name, (TO_DAYS(NOW())-TO_DAYS(birth))/365 AS age -> FROM pet ORDER BY name; +----------+------+ | name | age | +----------+------+ | Bowser | 9.58 | | Buffy | 9.88 | | Chirpy | 0.55 | | Claws | 5.04 | | Fang | 8.59 | | Fluffy | 6.15 | | Puffball | 0.00 | | Slim | 2.92 | | Whistler | 1.30 | +----------+------+ To sort the output by `age' rather than `name', just use a different `ORDER BY' clause: mysql> SELECT name, (TO_DAYS(NOW())-TO_DAYS(birth))/365 AS age -> FROM pet ORDER BY age; +----------+------+ | name | age | +----------+------+ | Puffball | 0.00 | | Chirpy | 0.55 | | Whistler | 1.30 | | Slim | 2.92 | | Claws | 5.04 | | Fluffy | 6.15 | | Fang | 8.59 | | Bowser | 9.58 | | Buffy | 9.88 | +----------+------+ A similar query can be used to determine age at death for animals that have died. You determine which animals these are by checking whether or not the `death' value is `NULL'. Then, for those with non-`NULL' values, compute the difference between the `death' and `birth' values: mysql> SELECT name, birth, death, (TO_DAYS(death)-TO_DAYS(birth))/365 AS age -> FROM pet WHERE death IS NOT NULL ORDER BY age; +--------+------------+------------+------+ | name | birth | death | age | +--------+------------+------------+------+ | Bowser | 1989-08-31 | 1995-07-29 | 5.91 | +--------+------------+------------+------+ The query uses `death IS NOT NULL' rather than `death != NULL' because `NULL' is a special value. This is explained later. *Note Working with `NULL': Working with NULL. What if you want to know which animals have birthdays next month? For this type of calculation, year and day are irrelevant; you simply want to extract the month part of the `birth' column. *MySQL* provides several date-part extraction functions, such as `YEAR()', `MONTH()', and `DAYOFMONTH()'. `MONTH()' is the appropriate function here. To see how it works, run a simple query that displays the value of both `birth' and `MONTH(birth)': mysql> SELECT name, birth, MONTH(birth) FROM pet; +----------+------------+--------------+ | name | birth | MONTH(birth) | +----------+------------+--------------+ | Fluffy | 1993-02-04 | 2 | | Claws | 1994-03-17 | 3 | | Buffy | 1989-05-13 | 5 | | Fang | 1990-08-27 | 8 | | Bowser | 1989-08-31 | 8 | | Chirpy | 1998-09-11 | 9 | | Whistler | 1997-12-09 | 12 | | Slim | 1996-04-29 | 4 | | Puffball | 1999-03-30 | 3 | +----------+------------+--------------+ Finding animals with birthdays in the upcoming month is easy, too. Suppose the current month is April. Then the month value is `4' and you look for animals born in May (month 5) like this: mysql> SELECT name, birth FROM pet WHERE MONTH(birth) = 5; +-------+------------+ | name | birth | +-------+------------+ | Buffy | 1989-05-13 | +-------+------------+ There is a small complication if the current month is December, of course. You don't just add one to the month number (`12') and look for animals born in month 13, because there is no such month. Instead, you look for animals born in January (month 1). You can even write the query so that it works no matter what the current month is. That way you don't have to use a particular month number in the query. `DATE_ADD()' allows you to add a time interval to a given date. If you add a month to the value of `NOW()', then extract the month part with `MONTH()', the result produces the month in which to look for birthdays: mysql> SELECT name, birth FROM pet -> WHERE MONTH(birth) = MONTH(DATE_ADD(NOW(), INTERVAL 1 MONTH)); A different way to accomplish the same task is to add `1' to get the next month after the current one (after using the modulo function (`MOD') to wrap around the month value to `0' if it is currently `12'): mysql> SELECT name, birth FROM pet -> WHERE MONTH(birth) = MOD(MONTH(NOW()), 12) + 1; Note that `MONTH' returns a number between 1 and 12. And `MOD(something,12)' returns a number between 0 and 11. So the addition has to be after the `MOD()' otherwise we would go from November (11) to January (1). Working with `NULL' Values .......................... The `NULL' value can be surprising until you get used to it. Conceptually, `NULL' means missing value or unknown value and it is treated somewhat differently than other values. To test for `NULL', you cannot use the arithmetic comparison operators such as `=', `<', or `!='. To demonstrate this for yourself, try the following query: mysql> SELECT 1 = NULL, 1 != NULL, 1 < NULL, 1 > NULL; +----------+-----------+----------+----------+ | 1 = NULL | 1 != NULL | 1 < NULL | 1 > NULL | +----------+-----------+----------+----------+ | NULL | NULL | NULL | NULL | +----------+-----------+----------+----------+ Clearly you get no meaningful results from these comparisons. Use the `IS NULL' and `IS NOT NULL' operators instead: mysql> SELECT 1 IS NULL, 1 IS NOT NULL; +-----------+---------------+ | 1 IS NULL | 1 IS NOT NULL | +-----------+---------------+ | 0 | 1 | +-----------+---------------+ In *MySQL*, 0 or `NULL' means false and anything else means true. The default truth value from a boolean operation is 1. This special treatment of `NULL' is why, in the previous section, it was necessary to determine which animals are no longer alive using `death IS NOT NULL' instead of `death != NULL'. Pattern Matching ................ *MySQL* provides standard SQL pattern matching as well as a form of pattern matching based on extended regular expressions similar to those used by Unix utilities such as `vi', `grep', and `sed'. SQL pattern matching allows you to use `_' to match any single character and `%' to match an arbitrary number of characters (including zero characters). In *MySQL*, SQL patterns are case insensitive by default. Some examples are shown below. Note that you do not use `=' or `!=' when you use SQL patterns; use the `LIKE' or `NOT LIKE' comparison operators instead. To find names beginning with `b': mysql> SELECT * FROM pet WHERE name LIKE "b%"; +--------+--------+---------+------+------------+------------+ | name | owner | species | sex | birth | death | +--------+--------+---------+------+------------+------------+ | Buffy | Harold | dog | f | 1989-05-13 | NULL | | Bowser | Diane | dog | m | 1989-08-31 | 1995-07-29 | +--------+--------+---------+------+------------+------------+ To find names ending with `fy': mysql> SELECT * FROM pet WHERE name LIKE "%fy"; +--------+--------+---------+------+------------+-------+ | name | owner | species | sex | birth | death | +--------+--------+---------+------+------------+-------+ | Fluffy | Harold | cat | f | 1993-02-04 | NULL | | Buffy | Harold | dog | f | 1989-05-13 | NULL | +--------+--------+---------+------+------------+-------+ To find names containing a `w': mysql> SELECT * FROM pet WHERE name LIKE "%w%"; +----------+-------+---------+------+------------+------------+ | name | owner | species | sex | birth | death | +----------+-------+---------+------+------------+------------+ | Claws | Gwen | cat | m | 1994-03-17 | NULL | | Bowser | Diane | dog | m | 1989-08-31 | 1995-07-29 | | Whistler | Gwen | bird | NULL | 1997-12-09 | NULL | +----------+-------+---------+------+------------+------------+ To find names containing exactly five characters, use the `_' pattern character: mysql> SELECT * FROM pet WHERE name LIKE "_____"; +-------+--------+---------+------+------------+-------+ | name | owner | species | sex | birth | death | +-------+--------+---------+------+------------+-------+ | Claws | Gwen | cat | m | 1994-03-17 | NULL | | Buffy | Harold | dog | f | 1989-05-13 | NULL | +-------+--------+---------+------+------------+-------+ The other type of pattern matching provided by *MySQL* uses extended regular expressions. When you test for a match for this type of pattern, use the `REGEXP' and `NOT REGEXP' operators (or `RLIKE' and `NOT RLIKE', which are synonyms). Some characteristics of extended regular expressions are: * `.' matches any single character. * A character class `[...]' matches any character within the brackets. For example, `[abc]' matches `a', `b', or `c'. To name a range of characters, use a dash. `[a-z]' matches any lowercase letter, whereas `[0-9]' matches any digit. * `*' matches zero or more instances of the thing preceding it. For example, `x*' matches any number of `x' characters, `[0-9]*' matches any number of digits, and `.*' matches any number of anything. * Regular expressions are case sensitive, but you can use a character class to match both lettercases if you wish. For example, `[aA]' matches lowercase or uppercase `a' and `[a-zA-Z]' matches any letter in either case. * The pattern matches if it occurs anywhere in the value being tested. (SQL patterns match only if they match the entire value.) * To anchor a pattern so that it must match the beginning or end of the value being tested, use `^' at the beginning or `$' at the end of the pattern. To demonstrate how extended regular expressions work, the `LIKE' queries shown above are rewritten below to use `REGEXP'. To find names beginning with `b', use `^' to match the beginning of the name: mysql> SELECT * FROM pet WHERE name REGEXP "^b"; +--------+--------+---------+------+------------+------------+ | name | owner | species | sex | birth | death | +--------+--------+---------+------+------------+------------+ | Buffy | Harold | dog | f | 1989-05-13 | NULL | | Bowser | Diane | dog | m | 1989-08-31 | 1995-07-29 | +--------+--------+---------+------+------------+------------+ Prior to *MySQL* Version 3.23.4, `REGEXP' is case sensitive, and the previous query will return no rows. To match either lowercase or uppercase `b', use this query instead: mysql> SELECT * FROM pet WHERE name REGEXP "^[bB]"; From *MySQL* 3.23.4 on, to force a `REGEXP' comparison to be case sensitive, use the `BINARY' keyword to make one of the strings a binary string. This query will match only lowercase `b' at the beginning of a name: mysql> SELECT * FROM pet WHERE name REGEXP BINARY "^b"; To find names ending with `fy', use `$' to match the end of the name: mysql> SELECT * FROM pet WHERE name REGEXP "fy$"; +--------+--------+---------+------+------------+-------+ | name | owner | species | sex | birth | death | +--------+--------+---------+------+------------+-------+ | Fluffy | Harold | cat | f | 1993-02-04 | NULL | | Buffy | Harold | dog | f | 1989-05-13 | NULL | +--------+--------+---------+------+------------+-------+ To find names containing a lowercase or uppercase `w', use this query: mysql> SELECT * FROM pet WHERE name REGEXP "w"; +----------+-------+---------+------+------------+------------+ | name | owner | species | sex | birth | death | +----------+-------+---------+------+------------+------------+ | Claws | Gwen | cat | m | 1994-03-17 | NULL | | Bowser | Diane | dog | m | 1989-08-31 | 1995-07-29 | | Whistler | Gwen | bird | NULL | 1997-12-09 | NULL | +----------+-------+---------+------+------------+------------+ Because a regular expression pattern matches if it occurs anywhere in the value, it is not necessary in the previous query to put a wild card on either side of the pattern to get it to match the entire value like it would be if you used a SQL pattern. To find names containing exactly five characters, use `^' and `$' to match the beginning and end of the name, and five instances of `.' in between: mysql> SELECT * FROM pet WHERE name REGEXP "^.....$"; +-------+--------+---------+------+------------+-------+ | name | owner | species | sex | birth | death | +-------+--------+---------+------+------------+-------+ | Claws | Gwen | cat | m | 1994-03-17 | NULL | | Buffy | Harold | dog | f | 1989-05-13 | NULL | +-------+--------+---------+------+------------+-------+ You could also write the previous query using the `{n}' "repeat-`n'-times" operator: mysql> SELECT * FROM pet WHERE name REGEXP "^.{5}$"; +-------+--------+---------+------+------------+-------+ | name | owner | species | sex | birth | death | +-------+--------+---------+------+------------+-------+ | Claws | Gwen | cat | m | 1994-03-17 | NULL | | Buffy | Harold | dog | f | 1989-05-13 | NULL | +-------+--------+---------+------+------------+-------+ Counting Rows ............. Databases are often used to answer the question, "How often does a certain type of data occur in a table?" For example, you might want to know how many pets you have, or how many pets each owner has, or you might want to perform various kinds of censuses on your animals. Counting the total number of animals you have is the same question as "How many rows are in the `pet' table?" because there is one record per pet. The `COUNT()' function counts the number of non-`NULL' results, so the query to count your animals looks like this: mysql> SELECT COUNT(*) FROM pet; +----------+ | COUNT(*) | +----------+ | 9 | +----------+ Earlier, you retrieved the names of the people who owned pets. You can use `COUNT()' if you want to find out how many pets each owner has: mysql> SELECT owner, COUNT(*) FROM pet GROUP BY owner; +--------+----------+ | owner | COUNT(*) | +--------+----------+ | Benny | 2 | | Diane | 2 | | Gwen | 3 | | Harold | 2 | +--------+----------+ Note the use of `GROUP BY' to group together all records for each `owner'. Without it, all you get is an error message: mysql> SELECT owner, COUNT(owner) FROM pet; ERROR 1140 at line 1: Mixing of GROUP columns (MIN(),MAX(),COUNT()...) with no GROUP columns is illegal if there is no GROUP BY clause `COUNT()' and `GROUP BY' are useful for characterizing your data in various ways. The following examples show different ways to perform animal census operations. Number of animals per species: mysql> SELECT species, COUNT(*) FROM pet GROUP BY species; +---------+----------+ | species | COUNT(*) | +---------+----------+ | bird | 2 | | cat | 2 | | dog | 3 | | hamster | 1 | | snake | 1 | +---------+----------+ Number of animals per sex: mysql> SELECT sex, COUNT(*) FROM pet GROUP BY sex; +------+----------+ | sex | COUNT(*) | +------+----------+ | NULL | 1 | | f | 4 | | m | 4 | +------+----------+ (In this output, `NULL' indicates sex unknown.) Number of animals per combination of species and sex: mysql> SELECT species, sex, COUNT(*) FROM pet GROUP BY species, sex; +---------+------+----------+ | species | sex | COUNT(*) | +---------+------+----------+ | bird | NULL | 1 | | bird | f | 1 | | cat | f | 1 | | cat | m | 1 | | dog | f | 1 | | dog | m | 2 | | hamster | f | 1 | | snake | m | 1 | +---------+------+----------+ You need not retrieve an entire table when you use `COUNT()'. For example, the previous query, when performed just on dogs and cats, looks like this: mysql> SELECT species, sex, COUNT(*) FROM pet -> WHERE species = "dog" OR species = "cat" -> GROUP BY species, sex; +---------+------+----------+ | species | sex | COUNT(*) | +---------+------+----------+ | cat | f | 1 | | cat | m | 1 | | dog | f | 1 | | dog | m | 2 | +---------+------+----------+ Or, if you wanted the number of animals per sex only for known-sex animals: mysql> SELECT species, sex, COUNT(*) FROM pet -> WHERE sex IS NOT NULL -> GROUP BY species, sex; +---------+------+----------+ | species | sex | COUNT(*) | +---------+------+----------+ | bird | f | 1 | | cat | f | 1 | | cat | m | 1 | | dog | f | 1 | | dog | m | 2 | | hamster | f | 1 | | snake | m | 1 | +---------+------+----------+ Using More Than one Table ......................... The `pet' table keeps track of which pets you have. If you want to record other information about them, such as events in their lives like visits to the vet or when litters are born, you need another table. What should this table look like? It needs: * To contain the pet name so you know which animal each event pertains to. * A date so you know when the event occurred. * A field to describe the event. * An event type field, if you want to be able to categorize events. Given these considerations, the `CREATE TABLE' statement for the `event' table might look like this: mysql> CREATE TABLE event (name VARCHAR(20), date DATE, -> type VARCHAR(15), remark VARCHAR(255)); As with the `pet' table, it's easiest to load the initial records by creating a tab-delimited text file containing the information: Fluffy 1995-05-15 litter 4 kittens, 3 female, 1 male Buffy 1993-06-23 litter 5 puppies, 2 female, 3 male Buffy 1994-06-19 litter 3 puppies, 3 female Chirpy 1999-03-21 vet needed beak straightened Slim 1997-08-03 vet broken rib Bowser 1991-10-12 kennel Fang 1991-10-12 kennel Fang 1998-08-28 birthday Gave him a new chew toy Claws 1998-03-17 birthday Gave him a new flea collar Whistler 1998-12-09 birthday First birthday Load the records like this: mysql> LOAD DATA LOCAL INFILE "event.txt" INTO TABLE event; Based on what you've learned from the queries you've run on the `pet' table, you should be able to perform retrievals on the records in the `event' table; the principles are the same. But when is the `event' table by itself insufficient to answer questions you might ask? Suppose you want to find out the ages of each pet when they had their litters. The `event' table indicates when this occurred, but to calculate the age of the mother, you need her birth date. Because that is stored in the `pet' table, you need both tables for the query: mysql> SELECT pet.name, (TO_DAYS(date) - TO_DAYS(birth))/365 AS age, remark -> FROM pet, event -> WHERE pet.name = event.name AND type = "litter"; +--------+------+-----------------------------+ | name | age | remark | +--------+------+-----------------------------+ | Fluffy | 2.27 | 4 kittens, 3 female, 1 male | | Buffy | 4.12 | 5 puppies, 2 female, 3 male | | Buffy | 5.10 | 3 puppies, 3 female | +--------+------+-----------------------------+ There are several things to note about this query: * The `FROM' clause lists two tables because the query needs to pull information from both of them. * When combining (joining) information from multiple tables, you need to specify how records in one table can be matched to records in the other. This is easy because they both have a `name' column. The query uses `WHERE' clause to match up records in the two tables based on the `name' values. * Because the `name' column occurs in both tables, you must be specific about which table you mean when referring to the column. This is done by prepending the table name to the column name. You need not have two different tables to perform a join. Sometimes it is useful to join a table to itself, if you want to compare records in a table to other records in that same table. For example, to find breeding pairs among your pets, you can join the `pet' table with itself to pair up males and females of like species: mysql> SELECT p1.name, p1.sex, p2.name, p2.sex, p1.species -> FROM pet AS p1, pet AS p2 -> WHERE p1.species = p2.species AND p1.sex = "f" AND p2.sex = "m"; +--------+------+--------+------+---------+ | name | sex | name | sex | species | +--------+------+--------+------+---------+ | Fluffy | f | Claws | m | cat | | Buffy | f | Fang | m | dog | | Buffy | f | Bowser | m | dog | +--------+------+--------+------+---------+ In this query, we specify aliases for the table name in order to refer to the columns and keep straight which instance of the table each column reference is associated with. Getting Information About Databases and Tables ============================================== What if you forget the name of a database or table, or what the structure of a given table is (for example, what its columns are called)? *MySQL* addresses this problem through several statements that provide information about the databases and tables it supports. You have already seen `SHOW DATABASES', which lists the databases managed by the server. To find out which database is currently selected, use the `DATABASE()' function: mysql> SELECT DATABASE(); +------------+ | DATABASE() | +------------+ | menagerie | +------------+ If you haven't selected any database yet, the result is blank. To find out what tables the current database contains (for example, when you're not sure about the name of a table), use this command: mysql> SHOW TABLES; +---------------------+ | Tables in menagerie | +---------------------+ | event | | pet | +---------------------+ If you want to find out about the structure of a table, the `DESCRIBE' command is useful; it displays information about each of a table's columns: mysql> DESCRIBE pet; +---------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +---------+-------------+------+-----+---------+-------+ | name | varchar(20) | YES | | NULL | | | owner | varchar(20) | YES | | NULL | | | species | varchar(20) | YES | | NULL | | | sex | char(1) | YES | | NULL | | | birth | date | YES | | NULL | | | death | date | YES | | NULL | | +---------+-------------+------+-----+---------+-------+ `Field' indicates the column name, `Type' is the data type for the column, `Null' indicates whether or not the column can contain `NULL' values, `Key' indicates whether or not the column is indexed, and `Default' specifies the column's default value. If you have indexes on a table, `SHOW INDEX FROM tbl_name' produces information about them. Examples of Common Queries ========================== Here are examples of how to solve some common problems with *MySQL*. Some of the examples use the table `shop' to hold the price of each article (item number) for certain traders (dealers). Supposing that each trader has a single fixed price per article, then (`item', `trader') is a primary key for the records. Start the command line tool `mysql' and select a database: mysql your-database-name (In most *MySQL* installations, you can use the database-name 'test'). You can create the example table as: CREATE TABLE shop ( article INT(4) UNSIGNED ZEROFILL DEFAULT '0000' NOT NULL, dealer CHAR(20) DEFAULT '' NOT NULL, price DOUBLE(16,2) DEFAULT '0.00' NOT NULL, PRIMARY KEY(article, dealer)); INSERT INTO shop VALUES (1,'A',3.45),(1,'B',3.99),(2,'A',10.99),(3,'B',1.45),(3,'C',1.69), (3,'D',1.25),(4,'D',19.95); Okay, so the example data is: mysql> SELECT * FROM shop; +---------+--------+-------+ | article | dealer | price | +---------+--------+-------+ | 0001 | A | 3.45 | | 0001 | B | 3.99 | | 0002 | A | 10.99 | | 0003 | B | 1.45 | | 0003 | C | 1.69 | | 0003 | D | 1.25 | | 0004 | D | 19.95 | +---------+--------+-------+ The Maximum Value for a Column ------------------------------ "What's the highest item number?" SELECT MAX(article) AS article FROM shop +---------+ | article | +---------+ | 4 | +---------+ The Row Holding the Maximum of a Certain Column ----------------------------------------------- "Find number, dealer, and price of the most expensive article." In ANSI SQL this is easily done with a sub-query: SELECT article, dealer, price FROM shop WHERE price=(SELECT MAX(price) FROM shop) In *MySQL* (which does not yet have sub-selects), just do it in two steps: 1. Get the maximum price value from the table with a `SELECT' statement. 2. Using this value compile the actual query: SELECT article, dealer, price FROM shop WHERE price=19.95 Another solution is to sort all rows descending by price and only get the first row using the *MySQL* specific `LIMIT' clause: SELECT article, dealer, price FROM shop ORDER BY price DESC LIMIT 1 *NOTE*: If there are several most expensive articles (for example, each 19.95) the `LIMIT' solution shows only one of them! Maximum of Column per Group --------------------------- "What's the highest price per article?" SELECT article, MAX(price) AS price FROM shop GROUP BY article +---------+-------+ | article | price | +---------+-------+ | 0001 | 3.99 | | 0002 | 10.99 | | 0003 | 1.69 | | 0004 | 19.95 | +---------+-------+ The Rows Holding the Group-wise Maximum of a Certain Field ---------------------------------------------------------- "For each article, find the dealer(s) with the most expensive price." In ANSI SQL, I'd do it with a sub-query like this: SELECT article, dealer, price FROM shop s1 WHERE price=(SELECT MAX(s2.price) FROM shop s2 WHERE s1.article = s2.article); In *MySQL* it's best do it in several steps: 1. Get the list of (article,maxprice). 2. For each article get the corresponding rows that have the stored maximum price. This can easily be done with a temporary table: CREATE TEMPORARY TABLE tmp ( article INT(4) UNSIGNED ZEROFILL DEFAULT '0000' NOT NULL, price DOUBLE(16,2) DEFAULT '0.00' NOT NULL); LOCK TABLES shop read; INSERT INTO tmp SELECT article, MAX(price) FROM shop GROUP BY article; SELECT shop.article, dealer, shop.price FROM shop, tmp WHERE shop.article=tmp.article AND shop.price=tmp.price; UNLOCK TABLES; DROP TABLE tmp; If you don't use a `TEMPORARY' table, you must also lock the 'tmp' table. "Can it be done with a single query?" Yes, but only by using a quite inefficient trick that I call the "MAX-CONCAT trick": SELECT article, SUBSTRING( MAX( CONCAT(LPAD(price,6,'0'),dealer) ), 7) AS dealer, 0.00+LEFT( MAX( CONCAT(LPAD(price,6,'0'),dealer) ), 6) AS price FROM shop GROUP BY article; +---------+--------+-------+ | article | dealer | price | +---------+--------+-------+ | 0001 | B | 3.99 | | 0002 | A | 10.99 | | 0003 | C | 1.69 | | 0004 | D | 19.95 | +---------+--------+-------+ The last example can, of course, be made a bit more efficient by doing the splitting of the concatenated column in the client. Using user variables -------------------- You can use *MySQL* user variables to remember results without having to store them in a temporary variables in the client. *Note Variables::. For example, to find the articles with the highest and lowest price you can do: select @min_price:=min(price),@max_price:=max(price) from shop; select * from shop where price=@min_price or price=@max_price; +---------+--------+-------+ | article | dealer | price | +---------+--------+-------+ | 0003 | D | 1.25 | | 0004 | D | 19.95 | +---------+--------+-------+ Using Foreign Keys ------------------ You don't need foreign keys to join 2 tables. The only thing *MySQL* doesn't do is `CHECK' to make sure that the keys you use really exist in the table(s) you're referencing and it doesn't automatically delete rows from table with a foreign key definition. If you use your keys like normal, it'll work just fine: CREATE TABLE persons ( id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT, name CHAR(60) NOT NULL, PRIMARY KEY (id) ); CREATE TABLE shirts ( id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT, style ENUM('t-shirt', 'polo', 'dress') NOT NULL, color ENUM('red', 'blue', 'orange', 'white', 'black') NOT NULL, owner SMALLINT UNSIGNED NOT NULL REFERENCES persons, PRIMARY KEY (id) ); INSERT INTO persons VALUES (NULL, 'Antonio Paz'); INSERT INTO shirts VALUES (NULL, 'polo', 'blue', LAST_INSERT_ID()), (NULL, 'dress', 'white', LAST_INSERT_ID()), (NULL, 't-shirt', 'blue', LAST_INSERT_ID()); INSERT INTO persons VALUES (NULL, 'Lilliana Angelovska'); INSERT INTO shirts VALUES (NULL, 'dress', 'orange', LAST_INSERT_ID()), (NULL, 'polo', 'red', LAST_INSERT_ID()), (NULL, 'dress', 'blue', LAST_INSERT_ID()), (NULL, 't-shirt', 'white', LAST_INSERT_ID()); SELECT * FROM persons; +----+---------------------+ | id | name | +----+---------------------+ | 1 | Antonio Paz | | 2 | Lilliana Angelovska | +----+---------------------+ SELECT * FROM shirts; +----+---------+--------+-------+ | id | style | color | owner | +----+---------+--------+-------+ | 1 | polo | blue | 1 | | 2 | dress | white | 1 | | 3 | t-shirt | blue | 1 | | 4 | dress | orange | 2 | | 5 | polo | red | 2 | | 6 | dress | blue | 2 | | 7 | t-shirt | white | 2 | +----+---------+--------+-------+ SELECT s.* FROM persons p, shirts s WHERE p.name LIKE 'Lilliana%' AND s.owner = p.id AND s.color <> 'white'; +----+-------+--------+-------+ | id | style | color | owner | +----+-------+--------+-------+ | 4 | dress | orange | 2 | | 5 | polo | red | 2 | | 6 | dress | blue | 2 | +----+-------+--------+-------+ Searching on Two Keys --------------------- *MySQL* doesn't yet optimize when you search on two different keys combined with `OR' (Searching on one key with different `OR' parts is optimized quite good): SELECT field1_index, field2_index FROM test_table WHERE field1_index = '1' OR field2_index = '1' The reason is that we haven't yet had time to come up with an efficient way to handle this in the general case. (The `AND' handling is, in comparison, now completely general and works very well). For the moment you can solve this very efficiently by using a `TEMPORARY' table. This type of optimization is also very good if you are using very complicated queries where the SQL server does the optimizations in the wrong order. CREATE TEMPORARY TABLE tmp SELECT field1_index, field2_index FROM test_table WHERE field1_index = '1'; INSERT INTO tmp SELECT field1_index, field2_index FROM test_table WHERE field2_index = '1'; SELECT * from tmp; DROP TABLE tmp; The above way to solve this query is in effect an `UNION' of two queries. Calculating visits per day -------------------------- The following shows an idea of how you can use the bit group functions to calculate the number of days per month a user has visited a web page. CREATE TABLE t1 (year YEAR(4), month INT(2) UNSIGNED ZEROFILL, day INT(2) UNSIGNED ZEROFILL); INSERT INTO t1 VALUES(2000,1,1),(2000,1,20),(2000,1,30),(2000,2,2),(2000,2,23),(2000,2,23); SELECT year,month,BIT_COUNT(BIT_OR(1< mysql < batch-file If you need to specify connection parameters on the command line, the command might look like this: shell> mysql -h host -u user -p < batch-file Enter password: ******** When you use `mysql' this way, you are creating a script file, then executing the script. Why use a script? Here are a few reasons: * If you run a query repeatedly (say, every day or every week), making it a script allows you to avoid retyping it each time you execute it. * You can generate new queries from existing ones that are similar by copying and editing script files. * Batch mode can also be useful while you're developing a query, particularly for multiple-line commands or multiple-statement sequences of commands. If you make a mistake, you don't have to retype everything. Just edit your script to correct the error, then tell `mysql' to execute it again. * If you have a query that produces a lot of output, you can run the output through a pager rather than watching it scroll off the top of your screen: shell> mysql < batch-file | more * You can catch the output in a file for further processing: shell> mysql < batch-file > mysql.out * You can distribute your script to other people so they can run the commands, too. * Some situations do not allow for interactive use, for example, when you run a query from a `cron' job. In this case, you must use batch mode. The default output format is different (more concise) when you run `mysql' in batch mode than when you use it interactively. For example, the output of `SELECT DISTINCT species FROM pet' looks like this when run interactively: +---------+ | species | +---------+ | bird | | cat | | dog | | hamster | | snake | +---------+ But like this when run in batch mode: species bird cat dog hamster snake If you want to get the interactive output format in batch mode, use `mysql -t'. To echo to the output the commands that are executed, use `mysql -vvv'. Queries from Twin Project ========================= At Analytikerna and Lentus, we have been doing the systems and field work for a big research project. This project is a collaboration between the Institute of Environmental Medicine at Karolinska Institutet Stockholm and the Section on Clinical Research in Aging and Psychology at the University of Southern California. The project involves a screening part where all twins in Sweden older than 65 years are interviewed by telephone. Twins who meet certain criteria are passed on to the next stage. In this latter stage, twins who want to participate are visited by a doctor/nurse team. Some of the examinations include physical and neuropsychological examination, laboratory testing, neuroimaging, psychological status assessment, and family history collection. In addition, data are collected on medical and environmental risk factors. More information about Twin studies can be found at: The latter part of the project is administered with a Web interface written using Perl and *MySQL*. Each night all data from the interviews are moved into a *MySQL* database. Find all Non-distributed Twins ------------------------------ The following query is used to determine who goes into the second part of the project: select concat(p1.id, p1.tvab) + 0 as tvid, concat(p1.christian_name, " ", p1.surname) as Name, p1.postal_code as Code, p1.city as City, pg.abrev as Area, if(td.participation = "Aborted", "A", " ") as A, p1.dead as dead1, l.event as event1, td.suspect as tsuspect1, id.suspect as isuspect1, td.severe as tsevere1, id.severe as isevere1, p2.dead as dead2, l2.event as event2, h2.nurse as nurse2, h2.doctor as doctor2, td2.suspect as tsuspect2, id2.suspect as isuspect2, td2.severe as tsevere2, id2.severe as isevere2, l.finish_date from twin_project as tp /* For Twin 1 */ left join twin_data as td on tp.id = td.id and tp.tvab = td.tvab left join informant_data as id on tp.id = id.id and tp.tvab = id.tvab left join harmony as h on tp.id = h.id and tp.tvab = h.tvab left join lentus as l on tp.id = l.id and tp.tvab = l.tvab /* For Twin 2 */ left join twin_data as td2 on p2.id = td2.id and p2.tvab = td2.tvab left join informant_data as id2 on p2.id = id2.id and p2.tvab = id2.tvab left join harmony as h2 on p2.id = h2.id and p2.tvab = h2.tvab left join lentus as l2 on p2.id = l2.id and p2.tvab = l2.tvab, person_data as p1, person_data as p2, postal_groups as pg where /* p1 gets main twin and p2 gets his/her twin. */ /* ptvab is a field inverted from tvab */ p1.id = tp.id and p1.tvab = tp.tvab and p2.id = p1.id and p2.ptvab = p1.tvab and /* Just the sceening survey */ tp.survey_no = 5 and /* Skip if partner died before 65 but allow emigration (dead=9) */ (p2.dead = 0 or p2.dead = 9 or (p2.dead = 1 and (p2.death_date = 0 or (((to_days(p2.death_date) - to_days(p2.birthday)) / 365) >= 65)))) and ( /* Twin is suspect */ (td.future_contact = 'Yes' and td.suspect = 2) or /* Twin is suspect - Informant is Blessed */ (td.future_contact = 'Yes' and td.suspect = 1 and id.suspect = 1) or /* No twin - Informant is Blessed */ (ISNULL(td.suspect) and id.suspect = 1 and id.future_contact = 'Yes') or /* Twin broken off - Informant is Blessed */ (td.participation = 'Aborted' and id.suspect = 1 and id.future_contact = 'Yes') or /* Twin broken off - No inform - Have partner */ (td.participation = 'Aborted' and ISNULL(id.suspect) and p2.dead = 0)) and l.event = 'Finished' /* Get at area code */ and substring(p1.postal_code, 1, 2) = pg.code /* Not already distributed */ and (h.nurse is NULL or h.nurse=00 or h.doctor=00) /* Has not refused or been aborted */ and not (h.status = 'Refused' or h.status = 'Aborted' or h.status = 'Died' or h.status = 'Other') order by tvid; Some explanations: `concat(p1.id, p1.tvab) + 0 as tvid' We want to sort on the concatenated `id' and `tvab' in numerical order. Adding `0' to the result causes *MySQL* to treat the result as a number. column `id' This identifies a pair of twins. It is a key in all tables. column `tvab' This identifies a twin in a pair. It has a value of `1' or `2'. column `ptvab' This is an inverse of `tvab'. When `tvab' is `1' this is `2', and vice versa. It exists to save typing and to make it easier for *MySQL* to optimize the query. This query demonstrates, among other things, how to do lookups on a table from the same table with a join (`p1' and `p2'). In the example, this is used to check whether a twin's partner died before the age of 65. If so, the row is not returned. All of the above exist in all tables with twin-related information. We have a key on both `id,tvab' (all tables), and `id,ptvab' (`person_data') to make queries faster. On our production machine (A 200MHz UltraSPARC), this query returns about 150-200 rows and takes less than one second. The current number of records in the tables used above: *Table* *Rows* `person_data' 71074 `lentus' 5291 `twin_project' 5286 `twin_data' 2012 `informant_data' 663 `harmony' 381 `postal_groups' 100 Show a Table on Twin Pair Status -------------------------------- Each interview ends with a status code called `event'. The query shown below is used to display a table over all twin pairs combined by event. This indicates in how many pairs both twins are finished, in how many pairs one twin is finished and the other refused, and so on. select t1.event, t2.event, count(*) from lentus as t1, lentus as t2, twin_project as tp where /* We are looking at one pair at a time */ t1.id = tp.id and t1.tvab=tp.tvab and t1.id = t2.id /* Just the sceening survey */ and tp.survey_no = 5 /* This makes each pair only appear once */ and t1.tvab='1' and t2.tvab='2' group by t1.event, t2.event; Using MySQL with Apache ======================= The Contrib section includes programs that let you authenticate your users from a *MySQL* database and also let you log your log files into a *MySQL* table. *Note Contrib::. You can change the Apache logging format to be easily readable by *MySQL* by putting the following into the Apache configuration file: LogFormat \ "\"%h\",%{%Y%m%d%H%M%S}t,%>s,\"%b\",\"%{Content-Type}o\", \ \"%U\",\"%{Referer}i\",\"%{User-Agent}i\"" In *MySQL* you can do something like this: LOAD DATA INFILE '/local/access_log' INTO TABLE table_name FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"' ESCAPED BY '\\' MySQL Database Administration ***************************** Configuring MySQL ================= mysqld Command-line Options --------------------------- `mysqld' accepts the following command-line options: `--ansi' Use ANSI SQL syntax instead of MySQL syntax. *Note ANSI mode::. `-b, --basedir=path' Path to installation directory. All paths are usually resolved relative to this. `--big-tables' Allow big result sets by saving all temporary sets on file. It solves most 'table full' errors, but also slows down the queries where in-memory tables would suffice. Since Version 3.23.2, *MySQL* is able to solve it automatically by using memory for small temporary tables and switching to disk tables where necessary. `--bind-address=IP' IP address to bind to. `--character-sets-dir=path' Directory where character sets are. *Note Character sets::. `--chroot=path' Chroot `mysqld' daemon during startup. Recommended security measure. It will somewhat limit `LOAD DATA INFILE' and `SELECT ... INTO OUTFILE' though. `--core-file' Write a core file if `mysqld' dies. For some systems you must also specify `--core-file-size' to `safe_mysqld'. *Note `safe_mysqld': safe_mysqld. `-h, --datadir=path' Path to the database root. `--default-character-set=charset' Set the default character set. *Note Character sets::. `--default-table-type=type' Set the default table type for tables. *Note Table types::. `--debug[...]=' If *MySQL* is configured with `--with-debug', you can use this option to get a trace file of what `mysqld' is doing. *Note Making trace files::. `--delay-key-write-for-all-tables' Don't flush key buffers between writes for any `MyISAM' table. *Note Server parameters::. `--enable-locking' Enable system locking. Note that if you use this option on a system which a not fully working lockd() (as on Linux) you will easily get mysqld to deadlock. `-T, --exit-info' This is a bit mask of different flags one can use for debugging the mysqld server; One should not use this option if one doesn't know exactly what it does! `--flush' Flush all changes to disk after each SQL command. Normally *MySQL* only does a write of all changes to disk after each SQL command and lets the operating system handle the syncing to disk. *Note Crashing::. `-?, --help' Display short help and exit. `--init-file=file' Read SQL commands from this file at startup. `-L, --language=...' Client error messages in given language. May be given as a full path. *Note Languages::. `-l, --log[=file]' Log connections and queries to file. *Note Query log::. `--log-isam[=file]' Log all ISAM/MyISAM changes to file (only used when debugging ISAM/MyISAM). `--log-slow-queries[=file]' Log all queries that have taken more than `long_query_time' seconds to execute to file. *Note Slow query log::. `--log-update[=file]' Log updates to `file.#' where `#' is a unique number if not given. *Note Update log::. `--log-long-format' Log some extra information to update log. If you are using `--log-slow-queries' then queries that are not using indexes are logged to the slow query log. `--low-priority-updates' Table-modifying operations (`INSERT'/`DELETE'/`UPDATE') will have lower priority than selects. It can also be done via `{INSERT | REPLACE | UPDATE | DELETE} LOW_PRIORITY ...' to lower the priority of only one query, or by `SET OPTION SQL_LOW_PRIORITY_UPDATES=1' to change the priority in one thread. *Note Table locking::. `--memlock' Lock the `mysqld' process in memory. This works only if your system supports the `mlockall()' system call (like Solaris). This may help if you have a problem where the operating system is causing `mysqld' to swap on disk. `--myisam-recover [=option[,option...]]] where option is any combination' of `DEFAULT', `BACKUP', `FORCE' or `QUICK'. You can also set this explicitely to `""' if you want to disable this option. If this option is used, `mysqld' will on open check if the table is marked as crashed or if if the table wasn't closed properly. (The last option only works if you are running with `--skip-locking'). If this is the case `mysqld' will run check on the table. If the table was corrupted, `mysqld' will attempt to repair it. The following options affects how the repair works. DEFAULT The same as not giving any option to `--myisam-recover'. BACKUP If the data table was changed during recover, save a backup of the `table_name.MYD' data file as `table_name-datetime.BAK'. FORCE Run recover even if we will loose more than one row from the .MYD file. QUICK Don't check the rows in the table if there isn't any delete blocks. Before a table is automatically repaired, *MySQL* will add a note about this in the error log. If you want to be able to recover from most things without user intervention, you should use the options `BACKUP,FORCE'. This will force a repair of a table even if some rows would be deleted, but it will keep the old data file as a backup so that you can later examine what happened. `--pid-file=path' Path to pid file used by `safe_mysqld'. `-P, --port=...' Port number to listen for TCP/IP connections. `-o, --old-protocol' Use the 3.20 protocol for compatibility with some very old clients. *Note Upgrading-from-3.20::. `--one-thread' Only use one thread (for debugging under Linux). *Note Debugging server::. `-O, --set-variable var=option' Give a variable a value. `--help' lists variables. You can find a full description for all variables in the `SHOW VARIABLES' section in this manual. *Note SHOW VARIABLES::. The tuning server parameters section includes information of how to optimize these. *Note Server parameters::. `--safe-mode' Skip some optimize stages. Implies `--skip-delay-key-write'. `--safe-show-database' Don't show databases for which the user doesn't have any privileges. `--safe-user-create' If this is enabled, a user can't create new users with the GRANT command, if the user doesn't have `INSERT' privilege to the `mysql.user' table or any column in this table. `--skip-concurrent-insert' Turn off the ability to select and insert at the same time on `MyISAM' tables. (This is only to be used if you think you have found a bug in this feature). `--skip-delay-key-write' Ignore the `delay_key_write' option for all tables. *Note Server parameters::. `--skip-grant-tables' This option causes the server not to use the privilege system at all. This gives everyone _full access_ to all databases! (You can tell a running server to start using the grant tables again by executing `mysqladmin flush-privileges' or `mysqladmin reload'.) `--skip-host-cache' Never use host name cache for faster name-ip resolution, but query DNS server on every connect instead. *Note DNS::. `--skip-locking' Don't use system locking. To use `isamchk' or `myisamchk' you must shut down the server. *Note Stability::. Note that in *MySQL* Version 3.23 you can use `REPAIR' and `CHECK' to repair/check `MyISAM' tables. `--skip-name-resolve' Hostnames are not resolved. All `Host' column values in the grant tables must be IP numbers or `localhost'. *Note DNS::. `--skip-networking' Don't listen for TCP/IP connections at all. All interaction with `mysqld' must be made via Unix sockets. This option is highly recommended for systems where only local requests are allowed. *Note DNS::. `--skip-new' Don't use new, possible wrong routines. Implies `--skip-delay-key-write'. This will also set default table type to `ISAM'. *Note ISAM::. `--skip-symlink' Don't delete or rename files that a symlinked file in the data directory points to. `--skip-safemalloc' If *MySQL* is configured with `--with-debug=full', all programs will check the memory for overruns for every memory allocation and memory freeing. As this checking is very slow, you can avoid this, when you don't need memory checking, by using this option. `--skip-show-database' Don't allow 'SHOW DATABASE' commands, unless the user has *process* privilege. `--skip-stack-trace' Don't write stack traces. This option is useful when you are running `mysqld' under a debugger. *Note Debugging server::. `--skip-thread-priority' Disable using thread priorities for faster response time. `--socket=path' Socket file to use for local connections instead of default `/tmp/mysql.sock'. `--sql-mode=option[,option[,option...]]' Option can be any combination of: `REAL_AS_FLOAT', `PIPES_AS_CONCAT', `ANSI_QUOTES', `IGNORE_SPACE', `SERIALIZE', `ONLY_FULL_GROUP_BY'. It can also be empty (`""') if you want to reset this. By specifying all of the above options is same as using -ansi. With this option one can turn on only needed SQL modes. *Note ANSI mode::. `transaction-isolation= { READ-UNCOMMITTED | READ-COMMITTED | REPEATABLE-READ | SERIALIZABLE }' Sets the default transaction isolation level. *Note SET TRANSACTION::. `-t, --tmpdir=path' Path for temporary files. It may be useful if your default `/tmp' directory resides on a partition too small to hold temporary tables. `-u, --user=user_name' Run `mysqld' daemon as user `user_name'. This option is _mandatory_ when starting `mysqld' as root. `-V, --version' Output version information and exit. `-W, --warnings' Print out warnings like `Aborted connection...' to the `.err' file. *Note Communication errors::. my.cnf Option Files ------------------- *MySQL* can, since Version 3.22, read default startup options for the server and for clients from option files. *MySQL* reads default options from the following files on Unix: *Filename* *Purpose* `/etc/my.cnf' Global options `DATADIR/my.cnf' Server-specific options `defaults-extra-file' The file specified with -defaults-extra-file=# `~/.my.cnf' User-specific options `DATADIR' is the *MySQL* data directory (typically `/usr/local/mysql/data' for a binary installation or `/usr/local/var' for a source installation). Note that this is the directory that was specified at configuration time, not the one specified with `--datadir' when `mysqld' starts up! (`--datadir' has no effect on where the server looks for option files, because it looks for them before it processes any command-line arguments.) *MySQL* reads default options from the following files on Windows: *Filename* *Purpose* `windows-system-directory\my.ini'Global options `C:\my.cnf' Global options `C:\mysql\data\my.cnf' Server-specific options Note that on Windows, you should specify all paths with `/' instead of `\'. If you use `\', you need to specify this twice, as `\' is the escape character in *MySQL*. *MySQL* tries to read option files in the order listed above. If multiple option files exist, an option specified in a file read later takes precedence over the same option specified in a file read earlier. Options specified on the command line take precedence over options specified in any option file. Some options can be specified using environment variables. Options specified on the command line or in option files take precedence over environment variable values. *Note Environment variables::. The following programs support option files: `mysql', `mysqladmin', `mysqld', `mysqldump', `mysqlimport', `mysql.server', `myisamchk', and `myisampack'. You can use option files to specify any long option that a program supports! Run the program with `--help' to get a list of available options. An option file can contain lines of the following forms: `#comment' Comment lines start with `#' or `;'. Empty lines are ignored. `[group]' `group' is the name of the program or group for which you want to set options. After a group line, any `option' or `set-variable' lines apply to the named group until the end of the option file or another group line is given. `option' This is equivalent to `--option' on the command line. `option=value' This is equivalent to `--option=value' on the command line. `set-variable = variable=value' This is equivalent to `--set-variable variable=value' on the command line. This syntax must be used to set a `mysqld' variable. The `client' group allows you to specify options that apply to all *MySQL* clients (not `mysqld'). This is the perfect group to use to specify the password you use to connect to the server. (But make sure the option file is readable and writable only by yourself.) Note that for options and values, all leading and trailing blanks are automatically deleted. You may use the escape sequences `\b', `\t', `\n', `\r', `\\', and `\s' in your value string (`\s' == blank). Here is a typical global option file: [client] port=3306 socket=/tmp/mysql.sock [mysqld] port=3306 socket=/tmp/mysql.sock set-variable = key_buffer_size=16M set-variable = max_allowed_packet=1M [mysqldump] quick Here is typical user option file: [client] # The following password will be sent to all standard MySQL clients password=my_password [mysql] no-auto-rehash set-variable = connect_timeout=2 [mysqlhotcopy] interactive-timeout If you have a source distribution, you will find sample configuration files named `my-xxxx.cnf' in the `support-files' directory. If you have a binary distribution, look in the `DIR/support-files' directory, where `DIR' is the pathname to the *MySQL* installation directory (typically `/usr/local/mysql'). Currently there are sample configuration files for small, medium, large, and very large systems. You can copy `my-xxxx.cnf' to your home directory (rename the copy to `.my.cnf') to experiment with this. All *MySQL* clients that support option files support the following options: -no-defaults Don't read any option files. -print-defaults Print the program name and all options that it will get. -defaults-file=full-path-to-default-fileOnly use the given configuration file. -defaults-extra-file=full-path-to-default-fileRead this configuration file after the global configuration file but before the user configuration file. Note that the above options must be first on the command line to work! `--print-defaults' may however be used directly after the `--defaults-xxx-file' commands. Note for developers: Option file handling is implemented simply by processing all matching options (that is, options in the appropriate group) before any command-line arguments. This works nicely for programs that use the last instance of an option that is specified multiple times. If you have an old program that handles multiply-specified options this way but doesn't read option files, you need add only two lines to give it that capability. Check the source code of any of the standard *MySQL* clients to see how to do this. In shell scripts you can use the `my_print_defaults' command to parse the config files: shell> my_print_defaults client mysql --port=3306 --socket=/tmp/mysql.sock --no-auto-rehash The above output contains all options for the groups 'client' and 'mysql'. Installing Many Servers on the Same Machine ------------------------------------------- In some cases you may want to have many different `mysqld' daemons (servers) running on the same machine. You may for example want to run a new version of *MySQL* for testing together with an old version that is in production. Another case is when you want to give different users access to different `mysqld' servers that they manage themselves. One way to get a new server running is by starting it with a different socket and port as follows: shell> MYSQL_UNIX_PORT=/tmp/mysqld-new.sock shell> MYSQL_TCP_PORT=3307 shell> export MYSQL_UNIX_PORT MYSQL_TCP_PORT shell> scripts/mysql_install_db shell> bin/safe_mysqld & The environment variables appendix includes a list of other environment variables you can use to affect `mysqld'. *Note Environment variables::. The above is the quick and dirty way that one commonly uses for testing. The nice thing with this is that all connections you do in the above shell will automatically be directed to the new running server! If you need to do this more permanently, you should create an option file for each server. *Note Option files::. In your startup script that is executed at boot time (mysql.server?) you should specify for both servers: `safe_mysqld --default-file=path-to-option-file' At least the following options should be different per server: `port=#' `socket=path' `pid-file=path' The following options should be different, if they are used: `log=path' `log-bin=path' `log-update=path' `log-isam=path' `bdb-logdir=path' If you want more performance, you can also specify the following differently: `tmpdir=path' `bdb-tmpdir=path' *Note Command-line options::. If you are installing binary *MySQL* versions (.tar files) and start them with `./bin/safe_mysqld' then in most cases the only option you need to add/change is the `socket' and `port' argument to `safe_mysqld'. Running Multiple MySQL Servers on the Same Machine -------------------------------------------------- There are circumstances when you might want to run multiple servers on the same machine. For example, you might want to test a new *MySQL* release while leaving your existing production setup undisturbed. Or you might be an Internet service provider that wants to provide independent *MySQL* installations for different customers. If you want to run multiple servers, the easiest way is to compile the servers with different TCP/IP ports and socket files so they are not both listening to the same TCP/IP port or socket file. *Note `mysqld_multi': mysqld_multi. Assume an existing server is configured for the default port number and socket file. Then configure the new server with a `configure' command something like this: shell> ./configure --with-tcp-port=port_number \ --with-unix-socket-path=file_name \ --prefix=/usr/local/mysql-3.22.9 Here `port_number' and `file_name' should be different than the default port number and socket file pathname, and the `--prefix' value should specify an installation directory different than the one under which the existing *MySQL* installation is located. You can check the socket used by any currently executing *MySQL* server with this command: shell> mysqladmin -h hostname --port=port_number variables Note that if you specify "`localhost'" as a hostname, `mysqladmin' will default to using Unix sockets instead of TCP/IP. If you have a *MySQL* server running on the port you used, you will get a list of some of the most important configurable variables in *MySQL*, including the socket name. You don't have to recompile a new *MySQL* server just to start with a different port and socket. You can change the port and socket to be used by specifying them at run time as options to `safe_mysqld': shell> /path/to/safe_mysqld --socket=file_name --port=port_number `mysqld_multi' can also take `safe_mysqld' (or `mysqld') as an argument and pass the options from a configuration file to `safe_mysqld' and further to `mysqld'. If you run the new server on the same database directory as another server with logging enabled, you should also specify the name of the log files to `safe_mysqld' with `--log', `--log-update', or `--log-slow-queries'. Otherwise, both servers may be trying to write to the same log file. *WARNING*: Normally you should never have two servers that update data in the same database! If your OS doesn't support fault-free system locking, this may lead to unpleasant surprises! If you want to use another database directory for the second server, you can use the `--datadir=path' option to `safe_mysqld'. *NOTE* also that starting several *MySQL* servers (`mysqlds') in different machines and letting them access one data directory over `NFS' is generally a *BAD IDEA*! The problem is that the `NFS' will become the bottleneck with the speed. It is not meant for such use. And last but not least, you would still have to come up with a solution how to make sure that two or more `mysqlds' are not interfering with each other. At the moment there is no platform that would 100% reliable do the file locking (`lockd' daemon usually) in every situation. Yet there would be one more possible risk with `NFS'; it would make the work even more complicated for `lockd' daemon to handle. So make it easy for your self and forget about the idea. The working solution is to have one computer with an operating system that efficiently handles threads and have several CPUs in it. When you want to connect to a *MySQL* server that is running with a different port than the port that is compiled into your client, you can use one of the following methods: * Start the client with `--host 'hostname' --port=port_number' to connect with TCP/IP, or `[--host localhost] --socket=file_name' to connect via a Unix socket. * In your C or Perl programs, you can give the port or socket arguments when connecting to the *MySQL* server. * If your are using the Perl `DBD::mysql' module you can read the options from the *MySQL* option files. *Note Option files::. $dsn = "DBI:mysql:test;mysql_read_default_group=client;mysql_read_default_file=/usr/local/mysql/data/my.cnf" $dbh = DBI->connect($dsn, $user, $password); * Set the `MYSQL_UNIX_PORT' and `MYSQL_TCP_PORT' environment variables to point to the Unix socket and TCP/IP port before you start your clients. If you normally use a specific socket or port, you should place commands to set these environment variables in your `.login' file. *Note Environment variables::. * Specify the default socket and TCP/IP port in the `.my.cnf' file in your home directory. *Note Option files::. General Security Issues and the MySQL Access Privilege System ============================================================= *MySQL* has an advanced but non-standard security/privilege system. This section describes how it works. General Security Guidelines --------------------------- Anyone using *MySQL* on a computer connected to the Internet should read this section to avoid the most common security mistakes. In discussing security, we emphasize the necessity of fully protecting the entire server host (not simply the *MySQL* server) against all types of applicable attacks: eavesdropping, altering, playback, and denial of service. We do not cover all aspects of availability and fault tolerance here. *MySQL* uses security based on Access Control Lists (ACLs) for all connections, queries, and other operations that a user may attempt to perform. There is also some support for SSL-encrypted connections between *MySQL* clients and servers. Many of the concepts discussed here are not specific to *MySQL* at all; the same general ideas apply to almost all applications. When running *MySQL*, follow these guidelines whenever possible: * DON'T EVER GIVE ANYONE (EXCEPT THE *MySQL* ROOT USER) ACCESS TO THE `user' TABLE IN THE `mysql' DATABASE! The encrypted password is the real password in *MySQL*. If you know the password listed in the `user' table for a given user, you can easily log in as that user if you have access to the host listed for that account. * Learn the *MySQL* access privilege system. The `GRANT' and `REVOKE' commands are used for controlling access to *MySQL*. Do not grant any more privileges than necessary. Never grant privileges to all hosts. Checklist: - Try `mysql -u root'. If you are able to connect successfully to the server without being asked for a password, you have problems. Anyone can connect to your *MySQL* server as the *MySQL* `root' user with full privileges! Review the *MySQL* installation instructions, paying particular attention to the item about setting a `root' password. - Use the command `SHOW GRANTS' and check to see who has access to what. Remove those privileges that are not necessary using the `REVOKE' command. * Do not keep any plain-text passwords in your database. When your computer becomes compromised, the intruder can take the full list of passwords and use them. Instead use `MD5()' or another one-way hashing function. * Do not choose passwords from dictionaries. There are special programs to break them. Even passwords like "xfish98" are very bad. Much better is "duag98" which contains the same word "fish" but typed one key to the left on a standard QWERTY keyboard. Another method is to use "Mhall" which is taken from the first characters of each word in the sentence "Mary had a little lamb." This is easy to remember and type, but difficult to guess for someone who does not know it. * Invest in a firewall. This protects you from at least 50% of all types of exploits in any software. Put *MySQL* behind the firewall or in a demilitarized zone (DMZ). Checklist: - Try to scan your ports from the Internet using a tool such as `nmap'. *MySQL* uses port 3306 by default. This port should be inaccessible from untrusted hosts. Another simple way to check whether or not your *MySQL* port is open is to try the following command from some remote machine, where `server_host' is the hostname of your *MySQL* server: shell> telnet server_host 3306 If you get a connection and some garbage characters, the port is open, and should be closed on your firewall or router, unless you really have a good reason to keep it open. If `telnet' just hangs or the connection is refused, everything is OK; the port is blocked. * Do not trust any data entered by your users. They can try to trick your code by entering special or escaped character sequences in Web forms, URLs, or whatever application you have built. Be sure that your application remains secure if a user enters something like "`; DROP DATABASE mysql;'". This is an extreme example, but large security leaks and data loss may occur as a result of hackers using similar techniques, if you do not prepare for them. Also remember to check numeric data. A common mistake is to protect only strings. Sometimes people think that if a database contains only publicly available data that it need not be protected. This is incorrect. At least denial-of-service type attacks can be performed on such databases. The simplest way to protect from this type of attack is to use apostrophes around the numeric constants: `SELECT * FROM table WHERE ID='234'' rather than `SELECT * FROM table WHERE ID=234'. *MySQL* automatically converts this string to a number and strips all non-numeric symbols from it. Checklist: - All Web applications: * Try to enter `'' and `"' in all your Web forms. If you get any kind of *MySQL* error, investigate the problem right away. * Try to modify any dynamic URLs by adding `%22' (`"'), `%23' (`#'), and `%27' (`'') in the URL. * Try to modify datatypes in dynamic URLs from numeric ones to character ones containing characters from previous examples. Your application should be safe against this and similar attacks. * Try to enter characters, spaces, and special symbols instead of numbers in numeric fields. Your application should remove them before passing them to *MySQL* or your application should generate an error. Passing unchecked values to *MySQL* is very dangerous! * Check data sizes before passing them to *MySQL*. * Consider having your application connect to the database using a different user name than the one you use for administrative purposes. Do not give your applications any more access privileges than they need. - Users of PHP: * Check out the `addslashes()' function. As of PHP 4.0.3, a `mysql_escape_string()' function is available that is based on the function of the same name in the *MySQL* C API. - Users of *MySQL* C API: * Check out the `mysql_escape_string()' API call. - Users of *MySQL*++: * Check out the `escape' and `quote' modifiers for query streams. - Users of Perl DBI: * Check out the `quote()' method or use placeholders. - Users of Java JDBC: * Use a `PreparedStatement' object and placeholders. * Do not transmit plain (unencrypted) data over the Internet. These da