Appendix D. SQL Syntax Reference

This appendix describes

• Each of the SQL statements provided by MySQL

• How to set and use user-defined variables within SQL statements

• The syntax for writing comments in SQL code. Comments are used to write descriptive text that is ignored by the server and to hide MySQL-specific keywords (these keywords will be executed by MySQL but ignored by other database servers).

MySQL development is ongoing, so enhancements to its SQL implementation are made on a continuing basis. You will find it useful to consult the online MySQL Reference Manual at http://www.mysql.com/ occasionally to see what new capabilities are being added.

The syntax descriptions use the following conventions:

• Optional information is enclosed in square brackets ([]).

• Vertical bars (|) separate alternative items in a list. If a list is enclosed in square brackets, one alternative may be chosen. If a list is enclosed in curly brackets ({}), one alternative must be chosen.

• Ellipsis notation (…) indicates that the term preceding the ellipsis can be repeated.

• n indicates an integer.

• 'string' indicates a string value. A single-quoted value such as 'file_name' or 'pattern' indicates a more specific kind of value, such as a filename or a pattern.

Unless otherwise indicated, the statements listed here have been present in MySQL at least as far back as MySQL 3.22.0.