SQL ( /ˈɛs kjuː ˈɛl/ "S-Q-L"; or "sequel"; or Structured Query Language) is a special-purpose programming language designed for managing data in relational database management systems (RDBMS).
Originally based upon relational algebra and tuple relational calculus, its scope includes data insert, query, update and delete, schema creation and modification, and data access control.
SQL was one of the first commercial languages for Edgar F. Codd's relational model, as described in his influential 1970 paper, "A Relational Model of Data for Large Shared Data Banks". Despite not adhering to the relational model as described by Codd, it became the most widely used database language. Although SQL is often described as, and to a great extent is, a declarative language, it 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.
Read more about SQL: History, Language Elements, Queries, Data Manipulation, Transaction Controls, Data Definition, Data Types, Data Control, Procedural Extensions, SQL Operators, Criticism, Standardization, Alternatives