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Developed at IBM in the early 1970s, SQL is an acronym for Structured Query Language, and it is used to manage data stored in a relational database.

Originally known as SEQUEL (Structured English Query Language), the language was designed to manipulate and retrieve data stored in IBM's System R, its quasi-relational database management system. The name was shortened to SQL because SEQUEL was trademarked by a UK company.

In the late 1970s and early 1980s, IBM developed a number of commercial products using their System R prototype. In the late 1970s, Relational Software, now known as Oracle Corporation, developed its own SQL-based RDMS for the US Navy, Central Intelligence Agency, and other government agencies, releasing the first commercial implementation of SQL, known as Oracle V2. ANSI and ISO standards for the language were adopted by 1986, and new versions of the standard were adopted in 1989, 1992, 1996, 2003, 2008, 2011, and 2016.

The sole purpose of SQL is to query data contained in a relational database. It is not an imperative programming language, like C or BASIC; rather, it is set-based and declarative.

Extensions have been written to add procedural programming language functionality to Standard SQL. Oracle's extension is PL/SQL. Others include ABAP, Mimer SQL, NZPLSQL, PL/PGSQL, PostgreSQL, PSQL, SPL, SQL PL, SQL/PSM, SQLScript, SSP, T-SQL, and Watcom-SQL, although some of these include several other features, as well, and are more than an extension of SQL.

The various implementations of SQL do not necessarily follow the full standards, and may be incompatible with one another, although Mime SQL and PostgreSQL come close.

The focus of this guide is in the SQL programming language and may include close implementations of the language, although some of these implementations are full programming languages, in their own right, and will be categorized separately. Additionally, any tools designed to facilitate programming in SQL are appropriate in this category, as are any SQL user groups, forums, tutorials, guides, or other resources.





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