MySql遞歸查詢（函數）

BEGIN
    DECLARE sTemp VARCHAR(1000);
    DECLARE sTempChd VARCHAR(1000);
    
    SET sTemp = '$';
    SET sTempChd =cast(_groupid as CHAR);
    WHILE sTempChd is not null DO
      SET sTemp = concat(sTemp,',',sTempChd);
SELECT group_concat(groupid) INTO sTempChd FROM group where FIND_IN_SET(up_groupid,sTempChd)>0;
END WHILE;
    RETURN sTemp;
 END