sql如何做递归层次查询

DROP FUNCTION IF EXISTS `WhlFucGetIDsOnID`;

CREATE DEFINER = `root`@`127.0.0.1` FUNCTION `WhlFucGetIDsOnID`(`inID` bigint)
 RETURNS text
BEGIN
	#Routine body goes here...
   DECLARE sTemp TEXT;
       DECLARE sTempChd TEXT; 

       SET sTemp = '$';
       SET sTempChd =cast(inID as CHAR); 

       WHILE sTempChd is not null DO
         SET sTemp = concat(sTemp,',',sTempChd);
         SELECT group_concat(jc_whatall.aid) INTO sTempChd FROM jc_whatall where FIND_IN_SET(jc_whatall.af,sTempChd)>0;
       END WHILE;
       RETURN sTemp;
END;

　以上代码参考：http://www.2cto.com/database/201209/152513.html，请尊重原作者。　

jc_whatall表结构