mysql分组排序

SELECT AA.ORDER_NO,AA.OPERATING_TIME,,AA.NEW_STATUS
FROM
(
SELECT R.ORDER_NO,R.OPERATING_TIME,R.NEW_STATUS,R.RANK
FROM
(
SELECT A.ORDER_NO,A.OPERATING_TIME,A.NEW_STATUS,
@rownum:=@rownum+1,
if(@pno=A.ORDER_NO,@rank:=@rank+1,@rank:=1) as rank,
@pno:=A.ORDER_NO
FROM
(
SELECT ORDER_NO,OPERATING_TIME,NEW_STATUS  FROM ORDER_STATUS_CHANGE_LOG a
WHERE OPERATING_TIME >= STR_TO_DATE('20160901','%Y%m%d')
ORDER BY ORDER_NO,OPERATING_TIME DESC
) A,
(select @rownum :=0 , @pno := null ,@rank:=0) B
) R
)AA
WHERE AA.RANK = 1;