Question

我有以下SQL：

DECLARE @ActualFromDT DATETIME,
        @ActualToDT DATETIME

IF (ManPowerUsage.FromDT >= Shift.FromDT)
    SET @ActualFromDT = ManPowerUsage.FromDT
ELSE
    SET @ActualFromDT =  Shift.FromDT

IF (ManPowerUsage.ToDT <= Shift.ToDT)
    SET @ActualToDT = ManPowerUsage.ToDT
ELSE
    SET @ActualToDT =  Shift.ToDT

SELECT Shift.ShiftID,
       Line.Line,
       ( SELECT SUM(DATEDIFF(MINUTE, @ActualFromDT, @ActualToDT))
              / DATEDIFF(MINUTE, Shift.FromDT, Shift.ToDT)

         FROM   ManPowerUsage

         WHERE  ManPowerUsage.LineID = Line.LineID
            AND ((Shift.FromDT < ManPowerUsage.FromDT AND Shift.ToDT > ManPowerUsage.FromDT) 
              OR (Shift.FromDT < ManPowerUsage.ToDT   AND Shift.ToDT > ManPowerUsage.ToDT  ))
            AND ManPowerUsage.IsEdited = 0
       ) AS ActualManpower
FROM ......

该命令显然不起作用，但我想知道如何在执行DATEDIFF之前设置参数

Answer 1

无处。您使用CASE expression作为“内联IF”

SELECT Shift.ShiftID,
   Line.Line,
   ( SELECT SUM(DATEDIFF(MINUTE,
               CASE
                  WHEN ManPowerUsage.FromDT >= Shift.FromDT
                         THEN ManPowerUsage.FromDT
                  ELSE Shift.FromDT
               END,
               CASE
                  WHEN ManPowerUsage.ToDT <= Shift.ToDT
                         THEN ManPowerUsage.ToDT
                  ELSE Shift.ToDT 
               END))
          / DATEDIFF(MINUTE, Shift.FromDT, Shift.ToDT)
...

Answer 2

你不应该需要任何变量，这样的事情就可以了。虽然没有完整的模式样本，SQL片段是不可测试的。

SELECT 
Shift.ShiftID, 
Line.Line, 
( SELECT SUM
    (
        DATEDIFF
        (
            MINUTE, 
            case when mpu.FromDT>Shift.FromDt then mpu.FromDT else Shift.FromDt end, 
            case when mpu.ToDT<=Shift.ToDt then mpu.ToDT else Shift.ToDt end
        )
    ) 
  / DATEDIFF(MINUTE, Shift.FromDT, Shift.ToDT) 
 FROM   ManPowerUsage mpu
 WHERE  mpu.LineID = Line.LineID 
 AND (
    (   Shift.FromDT < mpu.FromDT 
        AND Shift.ToDT > mpu.FromDT
    )  
    OR (    Shift.FromDT < mpu.ToDT   
            AND Shift.ToDT > mpu.ToDT  
        )
    )
 AND mpu.IsEdited = 0 
 ) AS ActualManpower

FROM ......

我应该在哪里放置IF块在这个SQL命令中

2 个答案: