Flag g causes the function to find each match in the string, not only the first one, and return a row for each such match. Beginning with Postgres 9.1 you can install the additional module pgtrgm to provide index support for any LIKE / ILIKE pattern (and simple regexp patterns. The flags parameter is an optional text string containing zero or more single-letter flags that change the function's behavior. The PostgreSQL REGEXPMATCHES () function matches a regular expression against a string and returns matched substrings. Using Regex in PostgreSQL Metacharacters Here is a quick cheat sheet for metacharacters to help define the pattern: Comparators There are three ways to use regex comparisons in SQL: LIKE SIMILAR TO POSIX comparators LIKE and SIMILAR TO are used for basic comparisons where you are looking for a matching string. If the pattern contains parenthesized subexpressions, the function returns a text array whose n'th element is the substring matching the n'th parenthesized subexpression of the pattern (not counting "non-capturing" parentheses see below for details). If the pattern contains no parenthesized subexpressions, then each row returned is a single-element text array containing the substring matching the whole pattern. If the pattern does not match, the function returns no rows. The function can return no rows, one row, or multiple rows (see the g flag below). It has the syntax regexp_matches(string, pattern ). The regexp_matches function returns a text array of all of the captured substrings resulting from matching a POSIX regular expression pattern. SELECT regexp_matches(column,'^stuff.*$')
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