SQL, SEQUEL (Structured English Query Language), is a language for RDBMS (Relational Database Management Systems). During the 1970s, a group at IBM's San Jose research center developed a database system "System R" based upon Codd's model. Structured English Query Language ("SEQUEL") was designed to manipulate and retrieve data stored in System R. The acronym SEQUEL was later condensed to SQL. SQL was adopted as a standard by ANSI (American National Standards Institute) in 1986 and ISO (International Organization for Standardization) in 1987. Since then, SQL standard has gone through a number of revisions:

* 1986, SQL-86 or SQL-87 - First published by ANSI. Ratified by ISO in 1987.

* 1989, SQL-89 - Minor revision.

* 1992, SQL-92 or SQL2 - Major revision (ISO 9075).

* 1999, SQL:1999 or SQL3 - Added regular expression matching, recursive queries, triggers, non-scalar types and some object-oriented features.

* 2003, SQL:2003 - Introduced XML-related features, window functions, standardized sequences and columns with auto-generated values (including identity-columns).

* 2006, SQL:2006 - ISO/IEC 9075-14:2006 defines ways in which SQL can be used in conjunction with XML.