摘要： CREATE OR REPLACE FUNCTION concat(character varying, character varying)RETURNS character varying AS$BODY$ DECLARE t varchar; BEGIN IF character_length($1) > 0 THEN t = $1||','|| $2; ELSE t = $2; END IF;RETURN t;END;$BODY$LANGUAGE plpgsql VOLATILECOST 100;ALTER FUNCTION concat(character va 阅读全文