Chapter 1. PostgreSQL SQL Reference

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The structured query language (SQL) is used by most relational databases to perform specific database operations. Before SQL came into existence, each database system used its own proprietary methods for accessing the underlying data. This caused many problems for developers who were trying to create portable front-end systems that could communicate with multiple databases.

The solution was to create a standard method of accessing database functions that each database vendor would support. The result was originally dubbed SQL-86, named after the year of its inception. Later, the standard was amended with additional features and renamed to SQL-89.

In 1992, the SQL specification was expanded significantly to handle extra data types, outer joins, catalog specification, and other enhancements. This version of SQL, called SQL-92 (a.k.a. SQL-2), is the foundation of many modern relational database management systems (RDBMSs).

PostgreSQL supports the majority of the functions outlined in the SQL-92 standard. The following pages list the SQL commands, their syntax, their options, and examples of how SQL is used in PostgreSQL. Although all the major functional specifications of SQL-92 are supported in PostgreSQL, there are occasions when PostgreSQL has SQL commands that have no counterpart in the formal SQL-92 specification. The following alphabetical listing notes these areas and points the user to synonymous commands.

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