SQL：从一组日期范围

Question

我正在尝试为我的问题找到合适的标题，到目前为止，它已经尝试了30分钟... :) 到目前为止，我有以下示例

DateFrom    DateTo   Amount 
2015/01/01 2015/08/31 1$ 
2015/01/01 2015/12/31 3$
2015/08/01 2015/12/31 7$

1. 对于第一行，我们得到0.125 $ /月（1 $ / 8个月）
2. 对于第二行，我们得到0.25美元/月（3 $ / 12个月）
3. 对于3d线，我们得到1.4美元/月（7 $ / 5个月）

考虑到上述情况，我们希望创建一组新的日期范围，以便获得金额的总和。类似下面的结果：

DateFrom    DateTo          Amount
2015/01/01 2015/07/31    (0.125$+0.25$)*7 =2.625$
2015/08/01 2015/08/31    (1.4$+0.125$+0.25$)*1  =1.775$
2015/09/01 2015/12/31    (1.4$+0.25$)*4   =6.6$

上述总和为11美元，就像原始数据一样。我们想要的结果实际上是每个唯一的日期范围组的金额之和。

这可以通过SQL实现吗？

Answer 1

解决方案不是很优雅，可能有一些不必要的部分，但它产生了正确的结果：

SELECT * INTO tbl_Periods
FROM ( VALUES
('2015/01/01','2015/08/31',1),
('2015/01/01','2015/12/31',3),
('2015/08/01','2015/12/31',7)) as x(DateFrom,DateTo,Amount);
GO
;WITH 
  Pass0 as (select 1 as C union all select 1),
  Pass1 as (select 1 as C from Pass0 as A, Pass0 as B),
  Pass2 as (select 1 as C from Pass1 as A, Pass1 as B),
  Pass3 as (select 1 as C from Pass2 as A, Pass2 as B)
, CTE1 as (
    SELECT *,  Amount / DateDiff(MONTH, DateFrom, DATEADD(day, 1 ,DateTo)) as MRate
    FROM tbl_Periods
)
, CTEM as (SELECT MIN(DateFrom) as MinDate,  DATEADD(day, 1, MAX(DateTo) ) as MaxDate
    ,  DateDiff(MONTH, MIN(DateFrom), DATEADD(day, 1, MAX(DateTo) )) as NPeriods FROM tbl_Periods)
, CTEP as (
    SELECT TOP ((SELECT NPeriods FROM CTEM)) ROW_NUMBER() OVER(ORDER BY (SELECT NULL)) as RNumber 
    FROM Pass3 as p
    )
, PeriodList as (
    SELECT DateAdd(month, RNumber-1,MinDate) as PeriodStarts, DateAdd(month, RNumber,DATEADD(day,-1,MinDate)) as PeriodEnds
    FROM CTEM as m CROSS JOIN CTEP as p)
, MPerriods as (
    SELECT * 
    FROM CTE1 as c 
    INNER JOIN PeriodList as l
    ON l.PeriodStarts between c.DateFrom and c.DateTo)
, CPeriods as (
    SELECT PeriodStarts, PeriodEnds, SUM(MRate) as MRate
        , RNK  = RANK() OVER(ORDER BY PeriodStarts)
            - RANK() OVER(PARTITION BY SUM(MRate) ORDER BY PeriodStarts)
    FROM MPerriods
    GROUP BY PeriodStarts, PeriodEnds
) 
SELECT MIN(PeriodStarts) as PeriodStarts, MAX(PeriodEnds) as PeriodEnds, COUNT(*) * MRate
FROM CPeriods
GROUP BY MRate, RNK
ORDER BY 1;
GO