Postgresql 中 根据ParentID 获取所有子 id

CREATE TABLE site2site
(
  id serial NOT NULL,
  siteid integer,
  parentid integer,
)

-- Function: getsitechild(id integer)

DROP FUNCTION getsitechild(id integer);

CREATE OR REPLACE FUNCTION getsitechild(id integer)
  RETURNS integer[]  AS
$BODY$
DECLARE
    cids integer[];
    childid integer;
BEGIN
    cids = array[]::integer[];
    for childid in select siteid from site2site where parentid = id loop
        cids = cids || childid;
        cids = cids || (select * from getsitechild(childid));
    end loop;
    return cids;
END;
$BODY$
  LANGUAGE 'plpgsql' VOLATILE
  COST 100;
ALTER FUNCTION getsitechild(id integer) OWNER TO postgres;