本文档描述了ISO/IEC 9075-1、ISO/IEC 9075-2和ISO/IEC 9075-11中定义的数据库语言SQL模型。该模型的各种概念的含义和之间的关系在文本中进行了描述，并以图形方式进行了说明。背景以一些历史回顾的形式和关键SQL特性的简要概述包括在内。 注2-尽管ISO/IEC 9075系列标准的名称包含短语“数据库语言”，但这些标准并没有使用单词“数据库”来描述SQL创建和操作的东西。“数据库”一词在许多不同的上下文中使用，其含义与ISO/IEC 9075系列的意图完全无关。因此，ISO/IEC 9075系列定义和使用了各种其他术语。“数据库”一词在本文档中经常非正式地用于表示“在任何给定时间由SQL实现管理的数据集合”。

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.”