Structured Query Language is a non-procedural language used to define, manipulate and retrieve data. It was developed by IBM (System/R project) in 1974-1979. The American National Standards Institute (ANSI) published in 1986 the first official standard of the language (later revised in 1989, 1992 and 1999), and since then, the industry has widely adopted SQL as the relational database language. Virtually every database system nowadays is interfaced through SQL.

The specific data architecture addressed by SQL is called the relational architecture. The various pieces of data (columns) are grouped into tables contained in databases, and we retrieve data using relations expressed between the tables.