去掉重复值，找出最新更改的数据（在先等）
sh ph cd rq
65X051270055 66.8020070315
65X051270055 66.3020070320
65X051270056 66.4020070315
65X051270056 65.9020070320
65X051270057 63.6020070315
65X051270057 63.1020070320
想查出sh,ph相同的情况的最后更新的数据，谢谢：）））
65X051270055 66.3020070320
65X051270056 65.9020070320
65X051270057 63.1020070320
[解决办法]
select a.* from tb a,
(select sh,ph , max(rq) rq from tb group by sh,ph) b
where a.sh = b.sh and a.ph = b.ph and a.rq = b.rq
[解决办法]
SELECT *
FROM TB A
WHERE NOT EXISTS
(SELECT 1 FROM TB WHERE A.SH=SH AND A.PH=PH AND RQ> A.RQ)
