Syntax: SQL Regular Expressions

The following syntax defines the SQL regular expression format.It is a complete and correct top-down definition.It is also highly formal and long, and may be daunting to anyone who hasn’t already some experience with regular expressions (or with highly formal, rather long top-down definitions).Feel free to skip it and read the next section, Building Regular Expressions, which uses a bottom-up approach, aimed at the rest of us.

<regular expression> ::= <regular term> ['|' <regular term> ...]

<regular term> ::= <regular factor> ...

<regular factor> ::= <regular primary> [<quantifier>]

<quantifier> ::= ? | * | + | '{' <m> [,[<n>]] '}'

<m>, <n> ::= unsigned int, with <m> <= <n> if both present

<regular primary> ::=
    <character> | <character class> | %
  | (<regular expression>)

<character> ::= <escaped character> | <non-escaped character>

<escaped character> ::=
  <escape-char> <special character> | <escape-char> <escape-char>

<special character> ::= any of the characters []()|^-+*%_?{}

<non-escaped character> ::=
  any character that is not a <special character>
  and not equal to <escape-char> (if defined)

<character class> ::=
    '_' | '[' <member> ... ']' | '[^' <non-member> ... ']'
  | '[' <member> ... '^' <non-member> ... ']'

<member>, <non-member> ::= <character> | <range> | <predefined class>

<range> ::= <character>-<character>

<predefined class> ::= '[:' <predefined class name> ':]'

<predefined class name> ::=
  ALPHA | UPPER | LOWER | DIGIT | ALNUM | SPACE | WHITESPACE