檢索當前月份和上個月的最後一條記錄

Question

我需要獲取當前月份和上個月的最後記錄值。每月大約有4,600條記錄。

以下是我已經嘗試了代碼，但它返回「0」爲兩個月，而不是價值：

SELECT a.LogPoint as [Meter] 
,max(CASE WHEN c.DateTimeStamp = dateadd(MM,-1,getdate()) THEN c.FloatVALUE ELSE 0 END) as [Total LAST Month] 
,max(CASE WHEN c.DateTimeStamp = getdate() THEN c.FloatVALUE ELSE 0 END) as [Total This Month] 
FROM 
    SWR.dbo.LoggedEntities a 
    ,SWR.dbo.TrendLogRelation b 
    ,SWR.dbo.LogTimeValues c 
WHERE 
     a.GUID = b .GUID 
    AND a.Type LIKE 'trend.ETLog' 
    AND a.LogPoint = 'WsumOut_Trnd' 
    AND b.EntityID = c.ParentID 
GROUP BY a.LogPoint 

任何幫助將不勝感激。
乾杯。

Answer 1

我假設LogPoint是主鍵。正確？在這種情況下，檢查以下內容：

SELECT mainA.LogPoint AS [Meter], 
     lastMonth.FloatValue AS [Total LAST Month], 
     thisMonth.FloatValue AS [Total This Month] 
FROM SWR.dbo.LoggedEntities mainA 
    CROSS APPLY 
    (
     SELECT TOP 1 c.FloatVALUE 
     FROM SWR.dbo.LoggedEntities a 
      JOIN SWR.dbo.TrendLogRelation b ON a.GUID = b.GUID 
      JOIN SWR.dbo.LogTimeValues c ON b.EntityID = c.ParentID 
     WHERE a.LogPoint = mainA.LogPoint 
     ORDER BY c.DateTimeStamp DESC 
    ) thisMonth 
    CROSS APPLY 
    (
     SELECT TOP 1 c.FloatVALUE 
     FROM SWR.dbo.LoggedEntities a 
      JOIN SWR.dbo.TrendLogRelation b ON a.GUID = b.GUID 
      JOIN SWR.dbo.LogTimeValues c ON b.EntityID = c.ParentID 
     WHERE a.LogPoint = mainA.LogPoint AND c.DateTimeStamp <= DATEADD(MM,-1,GETDATE()) 
     ORDER BY c.DateTimeStamp DESC 
    ) lastMonth 
WHERE a.Type LIKE 'trend.ETLog' 
     AND a.LogPoint = 'WsumOut_Trnd'; 

就意識到，我錯過了上個月日期檢查。現在添加。試試:)

Answer 2

getdate（）包括時間和日期，這就是爲什麼你沒有得到任何匹配。

一種選擇是將兩個值都轉換爲日期，然後進行比較。我開始前

Answer 3

兩個重要點：FROM子句中

1. 決不使用逗號。 總是使用明確的JOIN語法。
2. 表別名應該是表的縮寫。

然後，你要使用row_number()：

SELECT LogPoint as [Meter], 
     max(CASE WHEN seqnum = 1 AND 
        DATEDIFF(month, DateTimeStamp, getdate()) = 1 
       THEN cltv.FloatVALUE 
      END) as [Total LAST Month], 
     max(CASE WHEN seqnum = 1 AND 
        DATEDIFF(month, DateTimeStamp, getdate()) = 0 
       THEN ltv.FloatVALUE 
      END) as [Total This Month] 
FROM (SELECT le.LogPoint, ltv.DateTimeStamp, 
      ROW_NUMBER() OVER (PARTITION BY YEAR(DateTimeStamp), MONTH(DateTimeStamp) 
           ORDER BY DateTimeStamp DESC 
           ) as seqnum 
     FROM SWR.dbo.LoggedEntities le JOIN 
      SWR.dbo.TrendLogRelation tlr 
      ON le.GUID = tlr.GUID JOIN 
      SWR.dbo.LogTimeValues ltv 
      ON ltr.EntityID = ltv.ParentID 
     WHERE le.Type LIKE 'trend.ETLog' AND 
      le.LogPoint = 'WsumOut_Trnd' AND 
      DATEDIFF(month, ltv.DateTimeStamp, getdate()) IN (0, 1) 
    ) x 
WHERE seqnum = 1;