BNF Grammars

Backus-Naur Form (BNF) grammars are used as a tool for describing language and command syntax, for example:

select-statement : SELECT select-list FROM table-name [ restriction ] [ ordering ]

restriction : WHERE search-condition

ordering : ORDER BY sort-order

A BNF definition states that the named item given before the colon is written as described after the colon. For example, an ordering is written as ORDER BY followed by a sort-order (which may be defined elsewhere).

BNF expression	What it means
`named-construction` : `expression`	Declares that a named-construction is written as expression.
`named-construction` : `expression1` `expression2`	Declares that a named-construction is written as either expression1 or expression2.
`word`	The word `word`, written literally.
`exp1` `exp2`	exp1 followed by exp2.
`[exp]`	exp is optional.
`[ exp1 \| exp2 ]`	Either exp1 or exp2 or nothing.
`<exp>`	exp is an entity or name that you specify.
`exp` +	expression, repeated one or more times.
`exp` *	expression, repeated zero, one or more times.