This document describes the model of database language SQL as defined in ISO/IEC 9075-1, ISO/IEC 9075-2, and ISO/IEC 9075-11. The meanings of and the relationships between various concepts of that model are described in text and illustrated graphically. Background in the form of some historical review and a brief overview of key SQL features is included.

NOTE 2 — In spite of the fact that the names of the ISO/IEC 9075 series of standards contain the phrase “database language”, the standards do not use the word “database” to describe the thing that SQL creates and on which it operates. The word “database” is used in many different contexts and has meanings wholly unrelated to the intent of the ISO/IEC 9075 series. Consequently, a variety of other terms are defined and used by the ISO/IEC 9075 series. The word “database” is frequently used in this document informally to mean “a collection of data managed by an SQL-implementation at any given time.”