SQL equivalent of patindex in PostgreSQL

Question

I need the Postgres equivalent of patindex SQL function

Answer 1

There is no exact equivalent to SQL Server PATINDEX. You can use other string functions for your needs. Here are the docs: https://www.postgresql.org/docs/current/static/functions-string.html

But if you need exactly the same function, you can write a "wrapper" as shown below:

CREATE OR REPLACE FUNCTION "patindex"( "pattern" VARCHAR, "expression" VARCHAR ) RETURNS INT AS $BODY$
SELECT
    COALESCE(
        STRPOS(
             $2
            ,(
                SELECT
                    ( REGEXP_MATCHES(
                        $2
                        ,'(' || REPLACE( REPLACE( TRIM( $1, '%' ), '%', '.*?' ), '_', '.' ) || ')'
                        ,'i'
                    ) )[ 1 ]
                LIMIT 1
            )
        )
        ,0
    )
;
$BODY$ LANGUAGE 'sql' IMMUTABLE;

Example:

SELECT patindex( '%e_t%', 'Test String' );

2

SELECT patindex( '%S_r%', 'Test String' );

6

SELECT patindex( '%x%', 'Test String' );

0