MySQL

Screenshot of the default MySQL command line.
Developer(s)	MySQL AB
Initial release	May 23, 1995 (1995-05-23)
Stable release	5.1.41  (2009-11-05; 20 days ago) [+/−]
Preview release	5.4.3  (2009-10-06; 50 days ago) [+/−]
Written in	C, C++
Operating system	Cross-platform
Available in	English
Type	RDBMS
License	GNU General Public License (version 2, with linking exception) or proprietary EULA
Website	www.mysql.com

MySQL is a relational database management system (RDBMS)^[1] that has more than 6 million installations.^[2] MySQL stands for "My Structured Query Language". The program runs as a server providing multi-user access to a number of databases. MySQL is officially pronounced /maɪˌɛskjuːˈɛl/ (My S-Q-L), but often pronounced /maɪˌsiː'kwɛl/ (My SEQuel).^[3]

The project has made its source code available under the terms of the GNU General Public License, as well as under a variety of proprietary agreements. MySQL is owned and sponsored by a single for-profit firm, the Swedish company MySQL AB, now a subsidiary of Sun Microsystems^[4]. As of 2009^[update] Oracle Corporation began the process of acquiring Sun Microsystems.

MySQL is often used in free software projects that require a full-featured database management system, such as WordPress, phpBB and other software built on the LAMP software stack. It is also used in very high-scale World Wide Web products including Wikipedia, Google and Facebook^{[citation needed]}.

Contents 1 Uses 2 Platforms and interfaces 3 Features 3.1 Distinguishing features 3.2 Server compilation type 4 Product History 4.1 Future releases 5 Support and licensing 6 Corporate Backing History 7 See also 8 References 9 External links

[edit] Uses

Many web applications use MySQL as the database component of a LAMP software stack. Its popularity for use with web applications is closely tied to the popularity of PHP, which is often combined with MySQL. Several high-traffic web sites (including Flickr,^{[citation needed]} Facebook,^[5][6] Wikipedia^[7], Google^[8] (though not for searches), Nokia^{[citation needed]}, Auctionmarts and YouTube^{[citation needed]}) use MySQL for data storage and logging of user data.

[edit] Platforms and interfaces

MySQL code uses C and C++. The SQL parser uses yacc and a home-brewed lexer, sql_lex.cc^[9]

MySQL works on many different system platforms, including AIX, BSDi, FreeBSD, HP-UX, i5/OS, Linux, Mac OS X, NetBSD, Novell NetWare, OpenBSD, OpenSolaris, eComStation, OS/2 Warp, QNX, IRIX, Solaris, Symbian, SunOS, SCO OpenServer, SCO UnixWare, Sanos, Tru64 and Microsoft Windows. A port of MySQL to OpenVMS also exists.^[10]

All major programming languages with language-specific APIs include Libraries for accessing MySQL databases. In addition, an ODBC interface called MyODBC allows additional programming languages that support the ODBC interface to communicate with a MySQL database, such as ASP or ColdFusion. The MySQL server and official libraries are mostly implemented in ANSI C/ANSI C++.

To administer MySQL databases one can use the included command-line tool (commands: mysql and mysqladmin). Potential users may also download from the MySQL site: GUI administration tools: MySQL Administrator, MySQL Migration Toolkit and MySQL Query Browser. The GUI tools are now included in one package called MySQL GUI Tools.

In addition to the above-mentioned tools developed by MySQL AB, several other commercial and non-commercial tools integrate with MySQL. Examples include Navicat Free Lite Edition, AnySQL Maestro Freeware Edition or SQLyog Community Edition, they are free desktop based GUI tools, and phpMyAdmin, a free Web-based administration interface implemented in PHP.

[edit] Features

As of April 2009^[update], MySQL offers MySQL 5.1 in two different variants: the MySQL Community Server and Enterprise Server.^[11] They have a common code base and include the following features:

• A broad subset of ANSI SQL 99, as well as extensions
• Cross-platform support
• Stored procedures
• Triggers
• Cursors
• Updatable Views
• True Varchar support
• INFORMATION_SCHEMA
• Strict mode
• X/Open XA distributed transaction processing (DTP) support; two phase commit as part of this, using Oracle's InnoDB engine
• Independent storage engines (MyISAM for read speed, InnoDB for transactions and referential integrity, MySQL Archive for storing historical data in little space)
• Transactions with the InnoDB, BDB and Cluster storage engines; savepoints with InnoDB
• SSL support
• Query caching
• Sub-SELECTs (i.e. nested SELECTs)
• Replication support (i.e. Master-Master Replication & Master-Slave Replication) with one master per slave, many slaves per master, no automatic support for multiple masters per slave.
• Full-text indexing and searching using MyISAM engine
• Embedded database library
• Partial Unicode support (UTF-8 sequences longer than 3 bytes are not supported; UCS-2 encoded strings are also limited to the BMP)
• Partial ACID compliance (full compliance only when using the non-default storage engines InnoDB, BDB and Cluster)
• Shared-nothing clustering through MySQL Cluster
• Hot backup (via mysqlhotcopy) under certain conditions^[12]

The developers release monthly versions of the MySQL Enterprise Server and the sources can be obtained either from MySQL's customer-only Enterprise site or from MySQL's Bazaar repository, both under the GPL license. The MySQL Community Server is published on an unspecified schedule under the GPL and contains all bug fixes that were shipped with the last MySQL Enterprise Server release. Binaries are no longer provided by MySQL for every release of the Community Server.^[13][14]

[edit] Distinguishing features

MySQL implements the following features, which some other RDBMS systems may not:

• Multiple storage engines, allowing one to choose the one that is most effective for each table in the application (in MySQL 5.0, storage engines must be compiled in; in MySQL 5.1, storage engines can be dynamically loaded at run time):
  • Native storage engines (MyISAM, Falcon, Merge, Memory (heap), Federated, Archive, CSV, Blackhole, Cluster, Berkeley DB, EXAMPLE, and Maria)
  • Partner-developed storage engines (InnoDB, solidDB, NitroEDB, Infobright (formerly Brighthouse), Kickfire
  • Community-developed storage engines (memcached, httpd, PBXT, Revision Engine)
  • Custom storage engines
• Commit grouping, gathering multiple transactions from multiple connections together to increase the number of commits per second.

[edit] Server compilation type

Enterprise and Community users may deploy three types of MySQL Server Compilations:

• Standard: The MySQL-Standard binaries, recommended for most users, include the InnoDB storage engine.
• Max: (not MaxDB, a cooperation with SAP AG) is mysqld-max Extended MySQL Server. The MySQL-Max binaries include additional features that may not have been as extensively tested or are not required for general usage.
• The MySQL-Debug binaries, compiled with extra debug information, are not intended for production use, because the included debugging code may cause reduced performance.

Beginning with MySQL 5.1, MySQL AB has stopped providing these different package variants, and will standardize on one MySQL server package, which includes a mysqld binary with all functionality and storage engines enabled. Instead of providing a separate debug package, a server binary with extended debugging information is also included in the standard package.^[15]

[edit] Product History

Milestones in MySQL development include:

• Original development of MySQL by Michael Widenius and David Axmark beginning in 1994 ^[16]
• First internal release on 23 May 1995
• Windows version was released on 8 January 1998 for Windows 95 and NT
• Version 3.23: beta from June 2000, production release January 2001
• Version 4.0: beta from August 2002, production release March 2003 (unions)
• Version 4.01: beta from August 2003, Jyoti adopts MySQL for database tracking
• Version 4.1: beta from June 2004, production release October 2004 (R-trees and B-trees, subqueries, prepared statements)
• Version 5.0: beta from March 2005, production release October 2005 (cursors, stored procedures, triggers, views, XA transactions)

The developer of the Federated Storage Engine states that "The Federated Storage Engine is a proof-of-concept storage engine",^[17] but the main distributions of MySQL version 5.0 included it and turned it on by default. Documentation of some of the short-comings appears in "MySQL Federated Tables: The Missing Manual".

• Sun Microsystems acquired MySQL AB on 26 February 2008.^[4]
• Version 5.1: production release 27 November 2008 (event scheduler, partitioning, plugin API, row-based replication, server log tables)

Version 5.1 contained 20 known crashing and wrong result bugs in addition to the 35 present in version 5.0.^[18]

MySQL 5.1 and 6.0 showed poor performance when used for data warehousing — partly due to its inability to utilize multiple CPU cores for processing a single query.^[19].

[edit] Future releases

The MySQL 6 roadmap outlines support for:

• Referential integrity and Foreign key support for all storage engines is targeted for release in MySQL 6.1 (although it has been present since version 3.23.44 for InnoDB).
• Support for supplementary Unicode characters, beyond the 65,536 characters of the Basic Multilingual Plane (BMP); announced for MySQL 6.0.
• A new storage engine called Falcon. A preview of Falcon is available on MySQL's website.

The 2006 roadmap for future versions foreshadows support for parallelization.^[20]

[edit] Support and licensing

Via MySQL Enterprise MySQL AB offers support itself, including a 24/7 service with 30-minute response time. The support team has direct access to the developers as necessary to handle problems. In addition, it hosts forums and mailing lists, employees and other users are often available in several IRC channels providing assistance.

In addition to official product support from Sun, other companies offer support and services related to usage of MySQL. For example, Percona offers services related to optimization and Monty Program Ab offers non-recurring engineering.

Buyers of MySQL Enterprise have access to binaries and software certified for their particular operating system, and access to monthly binary updates with the latest bug-fixes. Several levels of Enterprise membership are available, with varying response times and features ranging from how to and emergency support through server performance tuning and system architecture advice. The MySQL Network Monitoring and Advisory Service monitoring tool for database servers is available only to MySQL Enterprise customers.

Potential users can install MySQL Server as free software under the GNU General Public License (GPL), and the MySQL Enterprise subscriptions include a GPL version of the server, with a traditional proprietary version available on request at no additional cost for cases where the intended use is incompatible with the GPL.^[21]

Both the MySQL server software itself and the client libraries use dual-licensing distribution. Users may choose the GPL,^[22] which MySQL has extended with a FLOSS License Exception. It allows Software licensed under other OSI-compliant Open Source licenses, which are not compatible to the GPL, to link against the MySQL client libraries.^[23]

Customers that do not wish to follow the terms of the GPL may choose to purchase a proprietary license.^[24]

Like many open-source programs, MySQL has trademarked its name, which others may use only with the trademark holder's permission.

[edit] Corporate Backing History

In October 2005, Oracle Corporation acquired Innobase OY, the Finnish company that developed the InnoDB storage engine that allows MySQL to provide such functionality as transactions and foreign keys. After the acquisition, an Oracle press release^[25] mentioned that the contracts that make the company's software available to MySQL AB would be due for renewal (and presumably renegotiation) some time in 2006. During the MySQL Users Conference in April 2006, MySQL issued a press release that confirmed that MySQL and Innobase OY agreed to a "multi-year" extension of their licensing agreement.^[26]

In February 2006, Oracle Corporation acquired Sleepycat Software,^[27] makers of the Berkeley DB, a database engine providing the basis for another MySQL storage engine.

In April 2009, Oracle Corporation entered into an agreement to purchase Sun Microsystems,^[28] current owners of the MySQL intellectual property. Sun's board of directors unanimously approved the deal, it was also approved by Sun's shareholders, and finally also U.S. government approved the deal on August 20, 2009.^[29]

[edit] See also

• Comparison of relational database management systems
• Drizzle
• Firebird (database server)
• HSQLDB
• Ingres (database)
• MySQL Workbench
• PostgreSQL

[edit] References

[edit] External links

Wikibooks has more on the topic of MySQL

Wikimedia Commons has media related to: MySQL

• MySQL database website
• MySQL site at Sun.com
• Planet MySQL - an aggregation of MySQL-related blogs
• Interview with David Axmark, MySQL co-founder Video
• MySQL Tutorial
• MySQL Certification
• MySQL at the Open Directory Project

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