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MYSQL

MySQL is a relational database management system (RDBMS) that runs as a server providing multi-user access to a number of databases. MySQL is officially pronounced /maɪˌɛskjuːˈɛl/ ("My S-Q-L"), but is often also pronounced /maɪˈsiːkwəl/ ("My Sequel"). It is named after developer Michael Widenius' daughter, My. The SQL phrase stands for Structured Query Language.

The MySQL development 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 was owned and sponsored by a single for-profit firm, the Swedish company MySQL AB, now owned by 'Oracle Corporation'.

Members of the MySQL community have created several forks (variations) such as Drizzle, OurDelta, Percona Server, and MariaDB. All of these forks were in progress before the Oracle acquisition; Drizzle was announced eight months before the Sun acquisition.

Free-software projects that require a full-featured database management system often use MySQL. Where the project may lead to something in commercial use, the license terms need careful study. Some free software project examples: WordPress, phpBB, Drupal and other software built on the LAMP software stack. MySQL is also used in many high-profile, large-scale World Wide Web products, including, Google and Facebook.

Uses

MySQL is a popular choice of database for use in web applications, and is a central component of the widely-used LAMP web application software stack — LAMP is an acronym for "Linux, Apache, MySQL, PHP". Its popularity is closely tied to the popularity of PHP. MySQL is used in some of the most frequently visited web sites on the Internet, including Flickr, Facebook, Google — though not for searches,Nokia.com and YouTube.

Platforms and interfaces

MySQL is written in C and C++. Its SQL parser is written in yacc, and a home-brewed lexical analyzer named sql_lex.cc.

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.

Many programming languages with language-specific APIs include libraries for accessing MySQL databases. These include MySQL Connector/Net for integration with Microsoft's Visual Studio (languages such as C# and VB are most commonly used) and the ODBC driver for Java. 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 HTSQL - URL based query method also ships with a MySQL adapter, allowing direct interaction between a MySQL database and any web client via structured URLs. The MySQL server and official libraries are mostly implemented in ANSI C/ANSI C++.

Management and graphical frontends

MySQL is primarily an RDBMS and therefore ships with no GUI tools to administer MySQL databases or manage data contained within. Users may use the included command-line tools, or download MySQL frontends from various parties that have developed desktop software and web applications to manage MySQL databases, build database structure, and work with data records.

Official

The official MySQL Workbench is a free integrated environment developed by MySQL AB, that enables users to graphically administer MySQL databases and visually design database structure. MySQL Workbench replaces the previous package of software, MySQL GUI Tools. Similar to other third-party packages, but still considered the authoritative MySQL frontend, MySQL Workbench lets users manage the following:

• Database design & modeling
  * SQL development — replacing MySQL Query Browser
  * Database administration — replacing MySQL Administrator

MySQL Workbench is available in two editions, the regular free and open source Community Edition which may be downloaded from the MySQL website, and the proprietary Standard Edition which extends and improves the feature set of the Community Edition.

Third-party

Several other third-party proprietary and free graphical administration applications (or "front ends") are available that integrate with MySQL and enable users to work with database structure and data visually. Some well-known front ends, in alphabetical order, are:

• Adminer — a free MySQL front end written in one PHP script, capable of managing multiple databases, with many CSS skins available.
  * DBEdit — a free front end for MySQL and other databases.
  * dbForge GUI Tools — a set of tools for database management that includes separate applications for schema comparison and synchronization, data comparison and synchronization, and building queries.
  * HeidiSQL — a full featured free front end that runs on Windows, and can connect to local or remote MySQL servers to manage databases, tables, column structure, and individual data records. Also supports specialised GUI features for date/time fields and enumerated multiple-value fields.
  * Navicat — a series of proprietary graphical database management applications, developed for Windows, Macintosh and Linux.
  * Other available proprietary MySQL front ends include Aqua Data Studio, dbForge Studio for MySQL, Epictetus, Oracle SQL Developer, SchemaBank, SQLyog, SQLPro SQL Client, Toad, Toad Data Modeler
  * Open Office — The database part of Open Office can manage MySQL databases. (You must install all of the Open Office suite. It is free and open source.)
  * phpMyAdmin — a free Web-based front end widely installed by Web hosts worldwide, since it is developed in PHP and is included in the convenient LAMP stack and WAMP software bundle installers.
  * MySql for Android — Lets you connect to a remote MySql database from your smartphone.

Command-line

MySQL ships with a suite of command-line tools for tasks such as querying the database, backing up data, inspecting status, performing common tasks such as creating a database, and many more. A variety of third-party command-line tools is also available, including:

• Maatkit, a set of power-user tools written in Perl
  * MySQL Sandbox, a set of scripts for quickly starting server instances for testing and development

Deployment

MySQL can be built and installed manually from source code, but this can be tedious so it is more commonly installed from a binary package unless special customizations are required. On most Linux distributions the package management system can download and install MySQL with minimal effort, though further configuration is often required to adjust security and optimization settings.

Though MySQL began as a low-end alternative to more powerful proprietary databases, it has gradually evolved to support higher-scale needs as well.

It is still most commonly used in small to medium scale single-server deployments, either as a component in a LAMP based web application or as a standalone database server. Much of MySQL's appeal originates in its relative simplicity and ease of use, which is enabled by an ecosystem of open source tools such as phpMyAdmin.

In the medium range, MySQL can be scaled by deploying it on more powerful hardware, such as a multi-processor server with gigabytes of memory.

There are however limits to how far performance can scale on a single server, so on larger scales, multi-server MySQL deployments are required to provide improved performance and reliability. A typical high-end configuration can include a powerful master database which handles data write operations and is replicated to multiple slaves that handle all read operations.The master server synchronizes continually with its slaves so in the event of failure a slave can be promoted to become the new master, minimizing downtime. Further improvements in performance can be achieved by caching the results from database queries in memory using memcached, or breaking down a database into smaller chunks called shards which can be spread across a number of distributed server clusters.

Features

As of April 2009, MySQL offers MySQL 5.1 in two different variants: the open source MySQL Community Server and the commercial Enterprise Server. 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[further explanation needed]
  * 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 and UCS-2 encoded strings are limited to the BMP)
  * Partial ACID compliance (full compliance only when using the non-default storage engines InnoDB, BDB and Cluster)
  * Partititoned tables with pruning of partitions in optimiser
  * Shared-nothing clustering through MySQL Cluster
  * Hot backup (via mysqlhotcopy) under certain conditions

The developers release monthly versions of the MySQL Server. The sources can be obtained from MySQL's web site or from MySQL's Bazaar repository, both under the GPL license.

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):
  o Native storage engines (MyISAM, Falcon, Merge, Memory (heap), Federated, Archive, CSV, Blackhole, Cluster, Berkeley DB, EXAMPLE, Maria, and InnoDB, which was made the default as of 5.5)
  o Partner-developed storage engines (solidDB, NitroEDB, Infobright (formerly Brighthouse), Kickfire, XtraDB, IBM DB2[22]). InnoDB used to be a partner-developed storage engine, but with recent acquisitions, Oracle now owns both MySQL core and InnoDB.
  o Community-developed storage engines (memcache engine, httpd, PBXT, Revision Engine)
  o Custom storage engines
  * Commit grouping, gathering multiple transactions from multiple connections together to increase the number of commits per second.

Product history

Milestones in MySQL development include:

• Original development of MySQL by Michael Widenius and David Axmark beginning in 1994
  * 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", 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.
  * 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 (almost all fixed as of release 5.1.51).
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.

• Oracle acquired Sun Microsystems on 27 January 2010. Oracle and Sun

• MySQL Server 5.5 is currently generally available (as of December 2010). Enhancements and features include:
  o The default storage engine is InnoDB, which supports transactions and referential integrity constraints.
  o Semisynchronous replication.
  o SIGNAL and RESIGNAL statement in compliance with the SQL standard.
  o Support for supplementary Unicode character sets utf16, utf32, and utf8mb4.
  o New options for user-defined partitioning.
  o Improved multi-core scalability

Future releases

MySQL Server 6.0.11-alpha was announced 22 May 2009 as the last release of the 6.0 line. Future MySQL Server development uses a New Release Model. Features developed for 6.0 are being incorporated into future releases.

Support and licensing

MySQL offers support via their MySQL Enterprise product, 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.

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.

Both the MySQL server software itself and the client libraries use dual-licensing distribution. Users may choose the GPL, 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.

Customers that do not wish to follow the terms of the GPL may purchase a proprietary license.

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

Corporate backing history

In October 2005, Oracle Corporation acquired Innobase OY, the Finnish company that developed the third-party InnoDB storage engine that allows MySQL to provide such functionality as transactions and foreign keys. After the acquisition, an Oracle press release 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.

In February 2006, Oracle Corporation acquired Sleepycat Software, makers of the Berkeley DB, a database engine providing the basis for another MySQL storage engine. This had little effect, as Berkeley DB was not widely used, and was deprecated (due to lack of use) in MySQL 5.1.12, a pre-GA release of MySQL 5.1 released in October 2006.

In January 2008, Sun Microsystems bought MySQL for US$1 billion.

In April 2009, Oracle Corporation entered into an agreement to purchase Sun Microsystems, then owners of MySQL copyright and trademark. Sun's board of directors unanimously approved the deal, it was also approved by Sun's shareholders, and by the U.S. government on August 20, 2009. On December 14, 2009, Oracle pledged to continue to enhance MySQL as it had done for the previous four years. A movement against Oracle's acquisition of MySQL, to "Save MySQL" from Oracle was started by one of the MySQL founders, Monty Widenius. The petition of 50,000+ developers and users called upon the European Commission to block approval of the acquisition. At the same time, several Free Software opinion leaders (including Eben Moglen, Pamela Jones of Groklaw, Jan Wildeboer and Carlo Piana, who also acted as co-counsel in the merger regulation procedure) advocated for the unconditional approval of the merger. As part of the negotiations with the European Commission, Oracle committed that MySQL server will continue to use the dual-licensing strategy long used by MySQL AB with commercial and GPL versions available until at least 2015. The Oracle acquisition was eventually unconditionally approved by the European Commission on January 21, 2010.Meanwhile, Monty Widenius has released a GPL only fork, MariaDB. MariaDB is based on the same code base as MySQL server and strives to maintain compatibility with Oracle provided versions.

Forks of MySQL

• Drizzle — a fork targeted at the web-infrastructure and cloud computing markets. The developers of the product describe it as a "smaller, slimmer and (hopefully) faster version of MySQL". As such is planned to have many common MySQL features stripped out, including stored procedures, query cache, prepared statements, views, and triggers. This is a complete rewrite of the server that does not maintain compatibility with MySQL.
  * MariaDB — a community-developed branch of the MySQL database, the impetus being the community maintenance of its free status under GPL as opposed to any uncertainty of MySQL license status under its current ownership by Oracle. The intent also being to maintain high fidelity with MySQL, ensuring a "drop-in" replacement capability with library binary equivalency and exacting matching with MySQL APIs and commands. It includes the XtraDB storage engine as a replacement for InnoDB.
  * Percona Server — a fork that includes the XtraDB storage engine. It is an enhanced version of MySQL that is fully compatible, and deviates as little as possible from it, while still providing beneficial new features, better performance, and improved instrumentation for analysis of performance and usage.
  * OurDelta — is best characterized as a source of binaries compiled with various patches, including patches from MariaDB, Percona, and Google.