My SQL查找上级方法

CREATE DEFINER=`root`@`%` FUNCTION `queryParentDepts`(parentId varchar(20)) RETURNS varchar(4000) CHARSET utf8
BEGIN

DECLARE sTemp VARCHAR(4000);
DECLARE sTempChd VARCHAR(4000);
declare count int;
set count=0;
SET sTemp = '$';
SET sTempChd = cast(parentId as char);
WHILE sTempChd is not NULL DO
set count=count+1;
if(count>=19) then
 set sTempChd=null;
 end if;
SELECT group_concat(parent_dept_code) INTO sTempChd FROM ehr_org.org_department where FIND_IN_SET(dept_code,sTempChd)>0;
if(sTempChd is null) then 
SET sTemp = sTemp;
else 
SET sTemp = CONCAT(sTemp,',',sTempChd);
end if;
END WHILE;
return sTemp;
END