[11] Since then, the standard has been revised multiple times to include a larger set of features and incorporate common extensions.

SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd[12] in the early 1970s.

[13] This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasirelational database management system, System R, which a group at IBM San Jose Research Laboratory had developed during the 1970s.

After moving to the San Jose Research Laboratory in 1973, they began work on a sequel to SQUARE.

[12] The original name SEQUEL, which is widely regarded as a pun on QUEL, the query language of Ingres,[14] was later changed to SQL (dropping the vowels) because "SEQUEL" was a trademark of the UK-based Hawker Siddeley Dynamics Engineering Limited company.

In June 1979, Relational Software introduced one of the first commercially available implementations of SQL, Oracle V2 (Version2) for VAX computers.

Several reasons for the lack of portability between database systems include: SQL was adopted as a standard by the ANSI in 1986 as SQL-86[26] and the ISO in 1987.

[27] The original standard declared that the official pronunciation for "SQL" was an initialism: /ˌɛsˌkjuːˈɛl/ ("ess cue el").

However, extensions to Standard SQL add procedural programming language functionality, such as control-of-flow constructs.

[40][41] An interactive user or program can issue SQL statements to a local RDB and receive tables of data and status indicators in reply from remote RDBs.

This is important for the efficient operation of application programs that issue complex, high-frequency queries.

The messages, protocols, and structural components of DRDA are defined by the Distributed Data Management Architecture.

SQL deviates in several ways from its theoretical foundation, the relational model and its tuple calculus.

Critics argue that SQL should be replaced with a language that returns strictly to the original foundation: for example, see The Third Manifesto by Hugh Darwen and C.J.

User-defined types are comparable to classes in object-oriented language with their own constructors, observers, mutators, methods, inheritance, overloading, overwriting, interfaces, and so on.