<pattern> within the <expression>. If the pattern does not match, returns NULL. If you want to extract all matches, use REGEXP_EXTRACT_ALL.
Syntax
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
"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).
"#Firebolt 2024"
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 2024" to be returned (same behavior as not setting this value, see the example above), while a 2 would return the second subgroup "2024".
"Firebolt"