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今天工作遇到，下面这段执行超慢，几乎不出来，在旧服务器上运行是可以的，一样代码，很快，在新虚拟服务器上，超慢。
select * from ( select RowNum=row_number() over(order by AutoId desc),StartTime,cast(testtime/1000.00 as decimal(10,2)) as testtime,AutoId from dbo.FTMaster M WITH(NOLock) Where StartTime >=‘2014-01-01 00:00:00.000‘ and StartTime <‘2014-12-31 23:00:00.000‘ and ModelIc=‘XXX‘ and Result=0 and TestType=3 and exists ( select AutoId from ( select Min(BB.autoid) AutoID
from (Select Max(StartTime) as starttime,SN From dbo.FTMaster WITH(NOLock)
Where StartTime >=‘2014-01-01 00:00:00.000‘ and StartTime <‘2014-12-31 23:00:00.000‘ and ModelIc=‘XXX‘ and TestType=3 group by Sn) as AA inner join
(Select AutoID,SN,StartTime From dbo.FTMaster WITH(NOLock)
Where StartTime >=‘2014-01-01 00:00:00.000‘ and StartTime <‘2014-12-31 23:00:00.000‘ and ModelIc=‘XXX‘ and TestType=3 ) As BB
on AA.SN=BB.SN And AA.StartTime=BB.StartTime group by BB.SN ) t where t.AutoId=M.AutoId ) ) as MasterTable WHERE RowNum between (1 - 1) * 12430 + 1 and 1 * 12430
执行里面的又很快， 为什么呢。
select RowNum=row_number() over(order by AutoId desc),StartTime,cast(testtime/1000.00 as decimal(10,2)) as testtime,AutoId from dbo.FTMaster M WITH(NOLock) Where StartTime >=‘2014-01-01 00:00:00.000‘ and StartTime <‘2014-12-31 23:00:00.000‘ and ModelIc=‘XXX‘ and Result=0 and TestType=3 and exists ( select AutoId from ( select Min(BB.autoid) AutoID from (Select Max(StartTime) as starttime,SN From dbo.FTMaster WITH(NOLock) Where StartTime >=‘2014-01-01 00:00:00.000‘ and StartTime <‘2014-12-31 23:00:00.000‘ and ModelIc=‘XXX‘ and TestType=3 group by Sn) as AA inner join (Select AutoID,SN,StartTime From dbo.FTMaster WITH(NOLock) Where StartTime >=‘2014-01-01 00:00:00.000‘ and StartTime <‘2014-12-31 23:00:00.000‘ and ModelIc=‘XXX‘ and TestType=3 ) As BB on AA.SN=BB.SN And AA.StartTime=BB.StartTime group by BB.SN ) t where t.AutoId=M.AutoId )
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原文地址：http://www.cnblogs.com/jjoo/p/4271075.html
