mysql 无限递归

BEGIN 
    DECLARE pTemp Varchar(21845);               
    DECLARE cTemp Varchar(21845);      -- 节点ID(临时变量)

    SET pTemp = '';  
    SET cTemp =cast(rootId as CHAR);  -- 把rootId强制转换为字符。
        
        WHILE cTemp is not null DO  
            SET pTemp = concat(pTemp,',',cTemp);  -- 把所有节点连接成字符串。
            SELECT GROUP_CONCAt(childid) INTO cTemp FROM ranks 
            WHERE FIND_IN_SET(parentid,cTemp)>0;
        END WHILE;  
        
    RETURN pTemp;  
END

    SELECT
                childid,parentId
            FROM 
                ranks T,
                (SELECT @DATAS := getChildId_bas_basic_tree (1404)) a
            WHERE find_in_set (childid, @DATAS);