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