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SQL - Wikipedia

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Structured Query Language (SQL) (pronounced/ˌɛsˌkjuˈɛl/S-Q-L; or alternatively as/ˈsiːkwəl/“sequel”)12 is a domain-specific language used to manage data, especially in a relational database management system (RDBMS). It is particularly useful in handling structured data, i.e., data incorporating relations among entities and variables.

Introduced in the 1970s, SQL offered two main advantages over older read–write APIs such as ISAM or VSAM. Firstly, it introduced the concept of accessing many records with one single command. Secondly, it eliminates the need to specify how to reach a record, i.e., with or without an index.

Originally based upon relational algebra and tuple relational calculus, SQL consists of many types of statements,3 which may be informally classed as sublanguages, commonly: data query language (DQL), data definition language (DDL), data control language (DCL), and data manipulation language (DML).4

The scope of SQL includes data query, data manipulation (insert, update, and delete), data definition (schema creation and modification), and data access control. Although SQL is essentially a declarative language (4GL), it also includes procedural elements.

SQL was one of the first commercial languages to use Edgar F. Codd’s relational model. The model was described in his influential 1970 paper, “A Relational Model of Data for Large Shared Data Banks”.5 Despite not entirely adhering to the relational model as described by Codd, SQL became the most widely used database language.67

SQL became a standard of the American National Standards Institute (ANSI) in 1986 and of the International Organization for Standardization (ISO) in 1987.8 Since then, the standard has been revised multiple times to include a larger set of features and incorporate common extensions. Despite the existence of standards, virtually no implementations in existence adhere to it fully, and most SQL code requires at least some changes before being ported to different database systems.

Printed 2026-06-28.

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Footnotes

  1. Beaulieu, Alan (April 2009). Mary E Treseler (ed.). Learning SQL (2nd ed.). Sebastopol, CA, USA: O’Reilly. ISBN 978-0-596-52083-0. ↩

  2. Chamberlin, Donald D.; Frana, Philip L. (3 October 2001). “Oral history interview with Donald D. Chamberlin”. University Digital Conservancy. hdl:11299/107215. Archived from the original on 24 February 2020. Retrieved 14 January 2020. We changed the original name “SEQUEL” to SQL because we got a letter from somebody’s lawyer that said the name “SEQUEL” belonged to them. We shortened it to SQL, for Structured Query Language, and the product was known as SQL/DS. ↩

  3. SQL-92, 4.22 SQL-statements, 4.22.1 Classes of SQL-statements “There are at least five ways of classifying SQL-statements:”, 4.22.2, SQL statements classified by function “The following are the main classes of SQL-statements:”; SQL:2003 4.11 SQL-statements, and later revisions. ↩

  4. Chatham, Mark (2012). Structured Query Language By Example - Volume I: Data Query Language. Lulu.com. p. 8. ISBN 978-1-291-19951-2. ↩

  5. Codd, Edgar F. (June 1970). “A Relational Model of Data for Large Shared Data Banks”. Communications of the ACM. 13 (6): 377–87. CiteSeerX 10.1.1.88.646. doi:10.1145/362384.362685. S2CID 207549016. ↩

  6. Chapple, Mike. “SQL Fundamentals”. Databases. About.com. Archived from the original on 22 February 2009. Retrieved 28 January 2009. ↩

  7. “Structured Query Language (SQL)”. International Business Machines. 27 October 2006. Retrieved 10 June 2007. ↩

  8. “ISO 9075:1987: Information technology – Database languages – SQL – Part 1: Framework (SQL/Framework)”. 1 June 2023. Retrieved 24 June 2025. ↩

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