Question

我们的实时项目有一个SQL Server 2012数据库，包括多个表和记录，基本上我们在一个表上有两个相同SQL查询的SQL查询问题。第一个SQL查询占用较少的执行时间，第二个SQL查询的执行速度非常慢。

我不知道为什么会有人帮助我解决这个问题？我们的两个问题如下......

首次查询（花费大量时间执行）：

SELECT * FROM (SELECT TOP 10 TrackerResponse.EventName,TrackerResponse.ReceiveTime,ISNull(TrackerResponse.InputStatus,0)  AS InputStatus,
                TrackerResponse.Latitude,TrackerResponse.Longitude,TrackerResponse.Speed,
                TrackerResponse.TrackerID,TrackerResponse.OdoMeter,TrackerResponse.Direction,
                UserCar.CarNo FROM TrackerResponse
                INNER JOIN UserCar ON (UserCar.TrackerID = TrackerResponse.TrackerID)
                WHERE  (TrackerResponse.EventName IS NOT NULL AND TrackerResponse.EventName<>'')
                AND TrackerResponse.TrackerID = 112 Order By ID DESC) AS Events)

第二次查询（减少执行时间）：

SELECT * FROM (SELECT TOP 10 TrackerResponse.EventName,TrackerResponse.ReceiveTime,ISNull(TrackerResponse.InputStatus,0)  AS InputStatus,
                TrackerResponse.Latitude,TrackerResponse.Longitude,TrackerResponse.Speed,
                TrackerResponse.TrackerID,TrackerResponse.OdoMeter,TrackerResponse.Direction,
                UserCar.CarNo FROM TrackerResponse
                INNER JOIN UserCar ON (UserCar.TrackerID = TrackerResponse.TrackerID)
                WHERE  (TrackerResponse.EventName IS NOT NULL AND TrackerResponse.EventName<>'')
                AND TrackerResponse.TrackerID = 56 Order By ID DESC) AS Events

Answer 1

我看到这两个查询都是类似的，但跟踪器ID的例外情况如此......我的最佳猜测是，此查询可能是Parameter sniffing的受害者..

尝试使用如下所示的选项（重新编译）来查看这是否是原因并按照上述链接中提到的文章进行解决

SELECT * FROM (SELECT TOP 10 TrackerResponse.EventName,TrackerResponse.ReceiveTime,ISNull(TrackerResponse.InputStatus,0)  AS InputStatus,
                TrackerResponse.Latitude,TrackerResponse.Longitude,TrackerResponse.Speed,
                TrackerResponse.TrackerID,TrackerResponse.OdoMeter,TrackerResponse.Direction,
                UserCar.CarNo FROM TrackerResponse
                INNER JOIN UserCar ON (UserCar.TrackerID = TrackerResponse.TrackerID)
                WHERE  (TrackerResponse.EventName IS NOT NULL AND TrackerResponse.EventName<>'')
                AND TrackerResponse.TrackerID = 56 Order By ID DESC
option(recompile) 
AS Events)

SQL Server查询问题

1 个答案: