两个日期的DateDiff在同一列SQL中

Question

使用Server 2005，我需要获得位于同一列中的2个日期的datediff，表如下所示：

OrderNo    OpNo    ResType    LoadedStartDate
-----------------------------------------------------
12345      1       PAINT      2014-05-01 00:00:00.000
12345      2       PAINT      2014-05-02 00:00:00.000
12345      3       PAINT      2014-05-03 00:00:00.000
12345      4       ASMB       2014-05-04 00:00:00.000
67890      1       PAINT      2014-05-02 00:00:00.000
67890      2       PAINT      2014-05-03 00:00:00.000
67890      3       PAINT      2014-05-04 00:00:00.000
67890      4       ASMB       2014-05-05 00:00:00.000

我需要获得OpNo 1和OpNo 4的日期差异，其中它们是相同的订单号。OpNo将永远是1和4，就像我试图比较的那样，ResType也是如此。

输出需要如下所示：

OrderNo    Difference
----------------------
12345      3
67890      3

(谢谢你的帮助:)

Answer 1

只需将表加入到自己的位置：

SELECT t1.OrderNo,DATEDIFF(day,t1.LoadedStartDate,t2.LoadedStartDate)
FROM UnnamedTableFromQuestion t1
       INNER JOIN
     UnnamedTableFromQuestion t2
       on
         t1.OrderNo = t2.OrderNo
WHERE t1.OpNo = 1 and
      t2.OpNo = 4

Answer 2

应该很简单

SELECT DATEDIFF(day, 
         (SELECT LoadedStartDate FROM Orders WHERE OrderNo = 12345 AND OpNo = 1),
         (SELECT LoadedStartDate FROM Orders WHERE OrderNo = 12345 AND OpNo = 4)
       )

因为内部选择返回标量值，所以它们可以用作DATEDIFF函数的参数。

要使此操作适用于表中的所有订单，您可以执行以下操作：

SELECT DISTINCT OrderNo, DATEDIFF(day, 
          (SELECT LoadedStartDate FROM Orders WHERE OrderNo = Ord.OrderNo AND OpNo = 1),
          (SELECT LoadedStartDate FROM Orders WHERE OrderNo = Ord.OrderNo AND OpNo = 4)
       ) AS Diff
FROM Orders Ord

演示： http://sqlfiddle.com/#!3/bc085/5

Answer 3

CTE在这样的场景中发挥着神奇的作用。对于您的需求，可以使用以下查询。

with op1
As
(
select orderno, opno, restype, LoadedStartDate From orders
where opno = 1
),
op4
As
(
select orderno, opno, restype, LoadedStartDate From orders
where opno = 4
)
select op1.orderno, datediff(day, op1.loadedstartdate, op4.loadedstartdate) DifferenceDays 
from op1 inner join op4 on op1.orderno = op4.orderno

希望它能帮上忙