[英]Optimize SQL Sub-Query for Max Value
我有以下查詢:
SELECT dlp.ParamID ParamID, dp.ParamName ParamName, dlp.LocID LocationID, ml.LocName LocationName , di.Entered_On DateEntered, dlp.FreqDays Frequency
FROM data_LocParams dlp
INNER JOIN data_Input di on dlp.LocID = di.LocID
INNER JOIN data_Parameters dp on dp.ParamID = di.ParamID
INNER JOIN map_Locations ml on ml.LocId = dlp.LocId
WHERE ( (dlp.FreqDays IS NOT NULL) AND di.Entered_On < (GETUTCDATE() - dlp.FreqDays))
AND
di.Entered_On = (select max(Entered_On ) from data_Input where LocId = dlp.LocID
and ParamId = dlp.ParamID)
我需要有關如何優化此查詢的幫助。 瓶頸似乎在以下方面:
di.Entered_On = (select max(Entered_On ) from data_Input where LocId = dlp.LocID
and ParamId = dlp.ParamID)
請注意,對於給定的Enter_On,我需要基於LocId和ParamId獲取Max Entered_On日期。
我嘗試了以下操作,但未獲得預期的結果:
SELECT * FROM
(
SELECT dlp.ParamID ParamID, dp.ParamName ParamName, dlp.LocID LocationID, ml.LocName LocationName, di.Entered_On DateEntered, dlp.FreqDays Frequency,
ROW_NUMBER() OVER (PARTITION BY dlp.LocId, dlp.ParamID
ORDER BY di.Entered_On DESC)
as RowNum
FROM data_LocParams dlp
INNER JOIN data_Input di on dlp.LocID = di.LocID
INNER JOIN data_Parameters dp on dp.ParamID = di.ParamID
INNER JOIN map_Locations ml on ml.LocId = dlp.LocId
WHERE dlp.FreqDays IS NOT NULL
) as a WHERE a.RowNum = 1 and DateEntered < (GETUTCDATE() - Frequency)
我認為您可以在di
表上將其替換為window函數(在此作為子查詢完成)。 請注意, where
子句不在子查詢中,因為這會影響用於max()
的行(這可能是第二個查詢中的問題):
SELECT dlp.ParamID ParamID, dp.ParamName ParamName, dlp.LocID LocationID, ml.LocName LocationName , di.Entered_On DateEntered, dlp.FreqDays Frequency
FROM data_LocParams dlp
INNER JOIN (select di.*,
max(Entered_On) over (partition by LocId, ParamId) as maxeo
from data_Input di
) di on dlp.LocID = di.LocID
INNER JOIN data_Parameters dp on dp.ParamID = di.ParamID
INNER JOIN map_Locations ml on ml.LocId = dlp.LocId
WHERE (dlp.FreqDays IS NOT NULL) AND di.Entered_On = di.maxeo and
di.Entered_On < (GETUTCDATE() - dlp.FreqDays)
嘗試像這樣使用-
select ParamID,
ParamName,
LocationID,
LocationName,
DateEntered,
Frequency
from (SELECT dlp.ParamID ParamID,
dp.ParamName ParamName,
dlp.LocID LocationID,
ml.LocName LocationName,
di.Entered_On DateEntered,
dlp.FreqDays Frequency,
row_number() over(partition by di.LocID order by di.Entered_On desc) as rn
FROM data_LocParams dlp
INNER JOIN data_Input di ON dlp.LocID = di.LocID
INNER JOIN data_Parameters dp ON dp.ParamID = di.ParamID
INNER JOIN map_Locations ml ON ml.LocId = dlp.LocId
WHERE ((dlp.FreqDays IS NOT NULL) AND di.Entered_On < (GETUTCDATE() - dlp.FreqDays))
) as T
where rn = 1
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.