Question

我需要从当前月份和上个月获得最后记录的值。每月大约有4,600条记录。

以下是我尝试过的代码，但它会返回＆＃39; 0＆＃39;这两个月而不是价值：

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

非常感谢任何帮助欢呼声。

Answer 1

我认为LogPoint是主键。正确？在这种情况下，请检查以下内容：

    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';

刚才意识到我错过了上个月的日期检查。现在补充道。尝试：）

Answer 2

getdate（）包括时间和日期，这就是为什么你没有得到任何匹配。

一种选择是将两个值都转换为日期，然后进行比较。

Answer 3

我开始之前的两个要点：

从不在FROM子句中使用逗号。始终使用明确的JOIN语法。
表别名应为表格的缩写。

然后，您想使用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;

从当前月份和上个月检索最后一条记录

3 个答案: