REGEXP_EXTRACT

Returns the first match of <pattern> within the <expression>. If the pattern does not match, returns NULL. If you want to extract all matches, use REGEXP_EXTRACT_ALL.

Syntax

REGEXP_EXTRACT(<expression>, <pattern>[,'<flag>[...]',[<index>]])

Parameters

Parameter	Description	Supported input types
`<expression>`	The string from which to extract a substring, based on a regular expression.	`TEXT`
`<pattern`	A re2 regular expression for matching with the string.	`TEXT`
`<flag>`	Optional. Flag that allows additional controls over the regular’s expression matching behavior. If using multiple flags, you can include them in the same single-quote block without any separator character.	Firebolt supports the following RE2 flags to override default matching behavior. With `-` in front, you can disable the flag. * `i` - Specifies case-insensitive matching. * `m` - Specifies multi-line mode. In this mode, `^` and `$` characters in the regex match the beginning and end of the line. * `s` - (Enabled per default) Specifies that the `.` metacharacter in regex matches the newline character in addition to any character in `.` * `U` - Specifies non-greedy mode. In this mode, the meaning of the metacharacters `` and `+` in regex `<pattern>` are swapped with `?` and `+?`, respectively. See the examples using flags below for the difference in how results are returned.
`<index>`	Optional. Indicates which subgroup of the expression match should be returned. The default value is `0` which means the whole match is returned, independent of any number of given subgroups.	An `INTEGER` between `0` and `N` where `N` is the number subgroups in the `<pattern>`.

Return Types

TEXT

Example

SELECT
	REGEXP_EXTRACT('ABC 2023', '^[A-Z]+');

Returns: "ABC"

Despite using subgroups in the regular expression, the full match will be returned as the optional <index> argument is not set (the default value 0 is used instead).

SELECT
	REGEXP_EXTRACT('Learning about #REGEX in #Firebolt 2023', '#([A-Za-z]+) (\\d+)');

Returns: "#Firebolt 2023"

The regular expression contains two subgroups which allows us to set the <index> argument to something between 0 and 2. Every other value will cause an exception to be thrown. Setting <index> to 0 would cause the full match "#Firebolt 2023" to be returned (same behavior as not setting this value, see the example above), while a 2 would return the second subgroup "2023".

SELECT
	REGEXP_EXTRACT('Learning about #REGEX in #Firebolt 2023', '#([a-z]+) (\\d+)', 'i', 1);

Returns: "Firebolt"