Regular Expressions

Name	Description
`regexp_extract(string, pattern[, group = 0][, options])`	If `string` contains the regexp `pattern`, returns the capturing group specified by optional parameter `group`. The `group` must be a constant value. If no `group` is given, it defaults to 0. A set of optional `options` can be set.
`regexp_extract(string, pattern, name_list[, options])`	If `string` contains the regexp `pattern`, returns the capturing groups as a struct with corresponding names from `name_list`.
`regexp_extract_all(string, regex[, group = 0][, options])`	Split the `string` along the `regex` and extract all occurrences of `group`.
`regexp_full_match(string, regex[, options])`	Returns `true` if the entire `string` matches the `regex`.
`regexp_matches(string, pattern[, options])`	Returns `true` if `string` contains the regexp `pattern`, `false` otherwise.
`regexp_replace(string, pattern, replacement[, options])`	If `string` contains the regexp `pattern`, replaces the matching part with `replacement`.
`regexp_split_to_array(string, regex[, options])`	Alias of `string_split_regex`. Splits the `string` along the `regex`.
`regexp_split_to_table(string, regex[, options])`	Splits the `string` along the `regex` and returns a row for each part.

`regexp_extract(string, pattern[, group = 0][, options])`

Description	If `string` contains the regexp `pattern`, returns the capturing group specified by optional parameter `group`. The `group` must be a constant value. If no `group` is given, it defaults to 0. A set of optional `options` can be set.
Example	`regexp_extract('abc', '([a-z])(b)', 1)`
Result	`a`

`regexp_extract(string, pattern, name_list[, options])`

Description	If `string` contains the regexp `pattern`, returns the capturing groups as a struct with corresponding names from `name_list`. A set of optional `options` can be set.
Example	`regexp_extract('2023-04-15', '(\d+)-(\d+)-(\d+)', ['y', 'm', 'd'])`
Result	`{'y':'2023', 'm':'04', 'd':'15'}`

`regexp_extract_all(string, regex[, group = 0][, options])`

Description	Split the `string` along the `regex` and extract all occurrences of `group`. A set of optional `options` can be set.
Example	`regexp_extract_all('hello_world', '([a-z ]+)_?', 1)`
Result	`[hello, world]`

`regexp_full_match(string, regex[, options])`

Description	Returns `true` if the entire `string` matches the `regex`. A set of optional `options` can be set.
Example	`regexp_full_match('anabanana', '(an)*')`
Result	`false`

`regexp_matches(string, pattern[, options])`

Description	Returns `true` if `string` contains the regexp `pattern`, `false` otherwise. A set of optional `options` can be set.
Example	`regexp_matches('anabanana', '(an)*')`
Result	`true`

`regexp_replace(string, pattern, replacement[, options])`

Description	If `string` contains the regexp `pattern`, replaces the matching part with `replacement`. A set of optional `options` can be set.
Example	`regexp_replace('hello', '[lo]', '-')`
Result	`he-lo`

`regexp_split_to_array(string, regex[, options])`

Description	Alias of `string_split_regex`. Splits the `string` along the `regex`. A set of optional `options` can be set.
Example	`regexp_split_to_array('hello world; 42', ';? ')`
Result	`['hello', 'world', '42']`

`regexp_split_to_table(string, regex[, options])`

Description	Splits the `string` along the `regex` and returns a row for each part. A set of optional `options` can be set.
Example	`regexp_split_to_table('hello world; 42', ';? ')`
Result	Three rows: `'hello'`, `'world', '42'`

The regexp_matches function is similar to the SIMILAR TO operator, however, it does not require the entire string to match. Instead, regexp_matches returns true if the string merely contains the pattern (unless the special tokens ^ and $ are used to anchor the regular expression to the start and end of the string). Below are some examples:

SELECT regexp_matches('abc', 'abc');       -- true
SELECT regexp_matches('abc', '^abc$');     -- true
SELECT regexp_matches('abc', 'a');         -- true
SELECT regexp_matches('abc', '^a$');       -- false
SELECT regexp_matches('abc', '.*(b|d).*'); -- true
SELECT regexp_matches('abc', '(b|c).*');   -- true
SELECT regexp_matches('abc', '^(b|c).*');  -- false
SELECT regexp_matches('abc', '(?i)A');     -- true
SELECT regexp_matches('abc', 'A', 'i');    -- true

Options for Regular Expression Functions

The regex functions support the following options.

Option	Description
`'c'`	case-sensitive matching
`'i'`	case-insensitive matching
`'l'`	match literals instead of regular expression tokens
`'m'`, `'n'`, `'p'`	newline sensitive matching
`'g'`	global replace, only available for `regexp_replace`
`'s'`	non-newline sensitive matching

For example:

SELECT regexp_matches('abcd', 'ABC', 'c'); -- false
SELECT regexp_matches('abcd', 'ABC', 'i'); -- true
SELECT regexp_matches('ab^/$cd', '^/$', 'l'); -- true
SELECT regexp_matches(E'hello\nworld', 'hello.world', 'p'); -- false
SELECT regexp_matches(E'hello\nworld', 'hello.world', 's'); -- true

Using `regexp_matches`

The regexp_matches operator will be optimized to the LIKE operator when possible. To achieve best performance, the 'c' option (case-sensitive matching) should be passed if applicable. Note that by default the RE2 library doesn't match the . character to newline.

Original	Optimized equivalent
`regexp_matches('hello world', '^hello', 'c')`	`prefix('hello world', 'hello')`
`regexp_matches('hello world', 'world$', 'c')`	`suffix('hello world', 'world')`
`regexp_matches('hello world', 'hello.world', 'c')`	`LIKE 'hello_world'`
`regexp_matches('hello world', 'he.*rld', 'c')`	`LIKE '%he%rld'`

Using `regexp_replace`

The regexp_replace function can be used to replace the part of a string that matches the regexp pattern with a replacement string. The notation \d (where d is a number indicating the group) can be used to refer to groups captured in the regular expression in the replacement string. Note that by default, regexp_replace only replaces the first occurrence of the regular expression. To replace all occurrences, use the global replace (g) flag.

Some examples for using regexp_replace:

SELECT regexp_replace('abc', '(b|c)', 'X');        -- aXc
SELECT regexp_replace('abc', '(b|c)', 'X', 'g');   -- aXX
SELECT regexp_replace('abc', '(b|c)', '\1\1\1\1'); -- abbbbc
SELECT regexp_replace('abc', '(.*)c', '\1e');      -- abe
SELECT regexp_replace('abc', '(a)(b)', '\2\1');    -- bac

Using `regexp_extract`

The regexp_extract function is used to extract a part of a string that matches the regexp pattern. A specific capturing group within the pattern can be extracted using the group parameter. If group is not specified, it defaults to 0, extracting the first match with the whole pattern.

SELECT regexp_extract('abc', '.b.');           -- abc
SELECT regexp_extract('abc', '.b.', 0);        -- abc
SELECT regexp_extract('abc', '.b.', 1);        -- (empty)
SELECT regexp_extract('abc', '([a-z])(b)', 1); -- a
SELECT regexp_extract('abc', '([a-z])(b)', 2); -- b

The regexp_extract function also supports a name_list argument, which is a LIST of strings. Using name_list, the regexp_extract will return the corresponding capture groups as fields of a STRUCT:

SELECT regexp_extract('2023-04-15', '(\d+)-(\d+)-(\d+)', ['y', 'm', 'd']);

{'y': 2023, 'm': 04, 'd': 15}

SELECT regexp_extract('2023-04-15 07:59:56', '^(\d+)-(\d+)-(\d+) (\d+):(\d+):(\d+)', ['y', 'm', 'd']);

{'y': 2023, 'm': 04, 'd': 15}

SELECT regexp_extract('duckdb_0_7_1', '^(\w+)_(\d+)_(\d+)', ['tool', 'major', 'minor', 'fix']);

Binder Error: Not enough group names in regexp_extract

If the number of column names is less than the number of capture groups, then only the first groups are returned. If the number of column names is greater, then an error is generated.

Limitations

Regular expressions only support 9 capture groups: \1, \2, \3, …, \9. Capture groups with two or more digits are not supported.