Contents
What does the regexp _ replace function do in PostgreSQL?
The regexp_replace function provides substitution of new text for substrings that match POSIX regular expression patterns. It has the syntax regexp_replace (source, pattern, replacement flags ]). The source string is returned unchanged if there is no match to the pattern.
How does pattern matching work in PostgreSQL 9.3?
The regexp_matches function returns a text array of all of the captured substrings resulting from matching a POSIX regular expression pattern. It has the syntax regexp_matches ( string, pattern [, flags ]). The function can return no rows, one row, or multiple rows (see the g flag below). If the pattern does not match, the function returns no rows.
Is there a default value for a cast in Postgres?
There is no default value for a CAST: A type cast specifies a conversion from one data type to another. PostgreSQL accepts two equivalent syntaxes for type casts: There is no room in the syntax for anything other than the expression to be casted and the desired target type.
Who is the author of regular expressions in PostgreSQL?
Regular Expression Details PostgreSQL ‘s regular expressions are implemented using a software package written by Henry Spencer. Much of the description of regular expressions below is copied verbatim from his manual.
How to match a pattern in POSIX regular expression?
The POSIX pattern language is described in much greater detail below. The substring function with two parameters, substring (string from pattern), provides extraction of a substring that matches a POSIX regular expression pattern. It returns null if there is no match, otherwise the portion of the text that matched the pattern.
How to skip expressions in a Postgres function?
CREATE OR REPLACE FUNCTION gridref_by_address (city text, country text) RETURNS SETOF research_db_gridreference AS $$ SELECT id, data, version FROM research_db_gridreference, jsonb_array_elements (data -> ‘addresses’) addresses WHERE ( addresses ->> ‘city’ = city AND addresses ->> ‘country’ = country ) $$ LANGUAGE sql STABLE;
How to match string in PostgreSQL regexp _ matches ( )?
The output contains the ‘#eduCBA’ and ‘#PostgreSQL’ string, which means matching strings with regular expression defined in pattern. In the above example, the regular expression is “ ( [A-Za-z0-9]+)”, which matches the string, which begins with a character hash (#) and is followed by any alphanumeric characters.
How to use substring ( ) with regular expressions in?
You can use regular expressions in the substring () function to extract a string that matches a specified pattern: Here is one example that uses POSIX regular expressions to extract any word that has ‘ss’ among its letters:
How are string functions used in PostgreSQL 8.3?
PostgreSQL also provides versions of these functions that use the regular function invocation syntax (see Table 9-7 ). Note: Before PostgreSQL 8.3, these functions would silently accept values of several non-string data types as well, due to the presence of implicit coercions from those data types to text.