pgsql编写触发器

CREATE OR REPLACE FUNCTION update_sub_towncode_insert()
   RETURNS "trigger" AS
$BODY$
begin
if(length(NEW.towncode)>0)
THEN
NEW.sub_towncode=subxzqhstr(NEW.towncode);
END IF;
RETURN NEW;
end
$BODY$
   LANGUAGE 'plpgsql' VOLATILE;
ALTER FUNCTION update_sub_towncode_insert() OWNER TO postgres;

    CREATE  TRIGGER update_sub_towncode_insert
   BEFORE INSERT
   ON poisexamine
   FOR EACH ROW
   EXECUTE PROCEDURE update_sub_towncode_insert();