PostgreSQL で配列と配列の差集合の配列を返す関数

create_function_array_minus.sql

--
-- SELECT array_minus(array[1,2,3], array[1,2]); -> {3}
--

CREATE OR REPLACE FUNCTION pg_temp.array_minus (anyarray, anyarray) RETURNS anyarray AS
$$
SELECT array_agg(t.unnest)
  FROM ((SELECT UNNEST($1))
         EXCEPT
        (SELECT UNNEST($2)))
    AS t;
$$
LANGUAGE SQL;