Page "Database" Paragraph 110

SQL was one of the first commercial languages for the relational model.

Despite not adhering to the relational model as described by Codd, it has become the most widely used database language.

Though often described as, and to a great extent is a declarative language, SQL also includes procedural elements.

SQL became a standard of the American National Standards Institute ( ANSI ) in 1986, and of the International Organization for Standards ( ISO ) in 1987.

Since then the standard has been enhanced several times with added features.

However, issues of SQL code portability between major RDBMS products still exist due to lack of full compliance with, or different interpretations of the standard.

Among the reasons mentioned are the large size, and incomplete specification of the standard, as well as vendor lock-in.