REGEXP_COUNT function - Amazon Redshift
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REGEXP_COUNT function

Searches a string for a regular expression pattern and returns an integer that indicates the number of times the specified pattern occurs in the string. If no match is found, then the function returns 0. For more information about regular expressions, see POSIX operators.

Syntax

REGEXP_COUNT( source_string, pattern [, position [, parameters ] ] )

Arguments

source_string

A CHAR or VARCHAR string.

pattern

A UTF-8 string literal that represents a regular expression pattern. For more information, see POSIX operators.

position

(Optional) A positive INTEGER that indicates the position within source_string to begin searching. The position is based on the number of characters, not bytes, so that multibyte characters are counted as single characters. The default is 1. If position is less than 1, the search begins at the first character of source_string. If position is greater than the number of characters in source_string, the result is 0.

parameters

(Optional) One or more string literals that indicate how the function matches the pattern. The possible values are the following:

  • c – Perform case-sensitive matching. The default is to use case-sensitive matching.

  • i – Perform case-insensitive matching.

  • p – Interpret the pattern with Perl Compatible Regular Expression (PCRE) dialect.

Return type

INTEGER

Examples

To count the number of times a three-letter sequence occurs, use the following example.

SELECT REGEXP_COUNT('abcdefghijklmnopqrstuvwxyz', '[a-z]{3}'); +--------------+ | regexp_count | +--------------+ | 8 | +--------------+

To count the occurrences of the string FOX using case-insensitive matching, use the following example.

SELECT REGEXP_COUNT('the fox', 'FOX', 1, 'i'); +--------------+ | regexp_count | +--------------+ | 1 | +--------------+

To use a pattern written in the PCRE dialect to locate words containing at least one number and one lowercase letter, use the following example. The example uses the ?= operator, which has a specific look-ahead connotation in PCRE. This example counts the number of occurrences of such words, with case-sensitive matching.

SELECT REGEXP_COUNT('passwd7 plain A1234 a1234', '(?=[^ ]*[a-z])(?=[^ ]*[0-9])[^ ]+', 1, 'p'); +--------------+ | regexp_count | +--------------+ | 2 | +--------------+

To use a pattern written in the PCRE dialect to locate words containing at least one number and one lowercase letter, use the following example. It uses the ?= operator, which has a specific connotation in PCRE. This example counts the number of occurrences of such words, but differs from the previous example in that it uses case-insensitive matching.

SELECT REGEXP_COUNT('passwd7 plain A1234 a1234', '(?=[^ ]*[a-z])(?=[^ ]*[0-9])[^ ]+', 1, 'ip'); +--------------+ | regexp_count | +--------------+ | 3 | +--------------+

The following example uses data from the USERS table in the TICKIT sample database. For more information, see Sample database.

To count the number of times the top-level domain name is either org or edu, use the following example.

SELECT email, REGEXP_COUNT(email,'@[^.]*\\.(org|edu)') FROM users ORDER BY userid LIMIT 4; +-----------------------------------------------+--------------+ | email | regexp_count | +-----------------------------------------------+--------------+ | Etiam.laoreet.libero@sodalesMaurisblandit.edu | 1 | | Suspendisse.tristique@nonnisiAenean.edu | 1 | | amet.faucibus.ut@condimentumegetvolutpat.ca | 0 | | sed@lacusUtnec.ca | 0 | +-----------------------------------------------+--------------+