计费周期日期范围

Question

代码：

DECLARE @CurrentDate DATE = '2018-01-02' ;  -- Can be any date. This is just a date I used as an anchor point.
DECLARE @BillingDayOfMonth INT = 31 ;       -- The day of the billing every month (can be between 1st and 31st of the month).

;WITH [TT1] ( [N] ) AS
    (
        SELECT  1
        UNION ALL
        SELECT  1
    )
    , [TT2] ( [N] ) AS
    (
        SELECT  1
        UNION ALL
        SELECT  1
        UNION ALL
        SELECT  1
        UNION ALL
        SELECT  1
        UNION ALL
        SELECT  1
        UNION ALL
        SELECT  1
    )
    , [TT] ( [N] ) AS
    (
        SELECT      ROW_NUMBER() OVER ( ORDER BY ( SELECT NULL ) )
        FROM        [TT1] [T1]
        CROSS JOIN  [TT2] [T2]
    )
SELECT  [N]
FROM    [TT] ; -- This gives me the count of 12 cycles (can vary).

目标： 返回当前和 X 个以前的计费周期日期（上例中总共 12 个周期）。

如果一个月内不存在 BillingDayOfMonth（即 29 日至 31 日，具体取决于月份），请选择该月的最后一天作为 BillingDayOfMonth。因此，如果 BillingDayOfMonth = 31st，则这一天在 11 月不存在。因此周期将在 @11/30 而不是 11/31 开始。上面的代码不完整，需要您帮助找出有效的解决方案。谢谢

期望的输出：

CycleStartDate  CycleEndDate
2017-12-31      2018-01-30      -- The most current cycle
2017-11-30      2017-12-30
2017-10-31      2017-11-29
2017-09-30      2017-10-30
2017-08-31      2017-09-29
2017-07-31      2017-08-30
2017-06-30      2017-07-30
2017-05-31      2017-06-29
2017-04-30      2017-05-30      -- Notice the EndDate
2017-03-31      2017-04-29      -- Notice the EndDate
2017-02-28      2017-03-30      -- Notice the StartDate
2017-01-31      2017-02-27      -- Notice the EndDate

Answer 1

因此，根据您的数字表方法和规则，您可以使用如下查询。

我针对 @BillingDayOfMonth 的值（例如 25、28、30）进行了测试，发现结果相当正确。

See live demo

DECLARE @CurrentDate DATE = '2018-01-02' ;  -- Can be any date. This is just a date I used as an anchor point.
DECLARE @BillingDayOfMonth INT = 31 ;       -- The day of the billing every month (can be between 1st and 31st of the month).
DECLARE @StartDate DATE
SET @StartDate=   CASE WHEN 
                       DAY(EOMONTH(@CurrentDate)) < @BillingDayOfMonth
                       THEN
                       EOMONTH(@CurrentDate)
                       ELSE
                       DATEFROMPARTS(YEAR(@CurrentDate),MONTH(@CurrentDate),@BillingDayOfMonth)
                   END

;WITH [TT1] ( [N] ) AS
    (
        SELECT  1
        UNION ALL
        SELECT  1
    )
    , [TT2] ( [N] ) AS
    (
        SELECT  1
        UNION ALL
        SELECT  1
        UNION ALL
        SELECT  1
        UNION ALL
        SELECT  1
        UNION ALL
        SELECT  1
        UNION ALL
        SELECT  1
    )
    , [TT] ( [N] ) AS
    (
        SELECT    
        ROW_NUMBER() OVER ( ORDER BY ( SELECT NULL ) )

        FROM        [TT1] [T1]
        CROSS JOIN  [TT2] [T2]
    )

SELECT  CycleStartDate  = 
                    DATEADD(M,-N,@StartDate)
        ,
        CycleEndDate    =
                    DATEADD(D,-1,DATEADD(M,1-N,@StartDate))

FROM    [TT] ;