距给定日期和频率最近的未来日期

Question

我有一个表格，上面有报告的开始日期和频率（每 1 个月、2 个月等。粒度为 1 个月）

我将如何创建一个选择来返回最近的未来报告的实际日期？

Example:  
startDate: 15.01.2015, frequency: 3 months  

if today is 03.01.2016 it should return 15.01.2016  
if today is 16.01.2016 it should return 15.04.2016

不能存储上次报告的日期。

编辑：请求的样本数据和预期结果：

Actual date is 05.01.2017

StartDate   Freq        Result
02.01.2016  1month      02.02.2017
06.01.2016  1month      06.01.2017
10.03.2016  3months     10.03.2017
01.01.2015  4months     01.05.2017

Answer 1

好吧，来玩数学吧。

计算从某个 StartDate 开始每 M 个月发生一次的事件的最近发生时间？

嗯，首先我计算整数除法和模数的余数，按频率计算，以防万一 MONTH(StartDate) = MONTH(ActualDate)

StartDate - ActualDate % Frequency

那么我需要知道报告被获取了多少次：

Occurrences = StartDate - ActualDate / Frequency

然后添加一个新的事件并乘以频率，您将得到应添加到 StartDate 的月数，注意当 DAY(StartDate)

(Occurrences + 1) * Frequency = Required month

create table #t (StartDate datetime, Freq varchar(10));
insert into #t values
('2016-01-02','1month'),
('2016-01-06','1month'),
('2016-03-10','3months'),
('2015-01-01','4months'),
('2016-01-06','3month');

DECLARE @ActualDate datetime;
SET @ActualDate = '2017-01-05'

SELECT @ActualDate as ActualDate;

;WITH Calc AS
(
    SELECT StartDate, Freq, CAST(LEFT(Freq, 1) AS Int) as intFreq,
           (DATEDIFF(month, StartDate, @ActualDate) / CAST(LEFT(Freq, 1) AS Int)) AS Occurrences,
           (DATEDIFF(month, StartDate, @ActualDate) % CAST(LEFT(Freq, 1) AS Int)) AS restIntDiv,
           DATEPART(day, StartDate) AS StartDay,
           DATEPART(day, @ActualDate) AS ActDay
    FROM #t
)
SELECT StartDate, Freq,
       CASE WHEN restIntDiv = 0 AND ActDay < StartDay
            THEN DATEADD(month, intFreq * (Occurrences), StartDate)
            ELSE DATEADD(month, intFreq * (Occurrences + 1), StartDate)
       END as [NextReport]
FROM Calc;

+---------------------+---------+---------------------+
|      StartDate      |   Freq  | NextReport          |
+---------------------+---------+---------------------+
| 02.01.2016 00:00:00 |  1month | 02.02.2017 00:00:00 |
+---------------------+---------+---------------------+
| 06.01.2016 00:00:00 |  1month | 06.01.2017 00:00:00 |
+---------------------+---------+---------------------+
| 10.03.2016 00:00:00 | 3months | 10.03.2017 00:00:00 |
+---------------------+---------+---------------------+
| 01.01.2015 00:00:00 | 4months | 01.05.2017 00:00:00 |
+---------------------+---------+---------------------+
| 06.01.2016 00:00:00 |  3month | 06.01.2017 00:00:00 |
+---------------------+---------+---------------------+

可以在这里查看：http://rextester.com/MBSM51925

Answer 2

我经常使用 TVF 来创建动态日期/时间范围。 Tally 表也可以解决问题。 UDF 比递归 CTE 更快（尤其是对于较大的集合）并提供更多功能。 Date Range、DatePart 和 Increments 是参数。

Declare @YourTable table (StartDate date,frequency varchar(25))
Insert Into @YourTable values
('2016-01-02','1month'),
('2016-01-06','1month'),
('2016-03-10','3months'),
('2015-01-01','4months')

Select A.*
      ,NextDate=cast(B.RetVal as date)
 From  @YourTable A
 Cross Apply (
                Select Top 1 * From [dbo].[udf-Range-Date](A.StartDate,'2025-01-15','MM',left(A.frequency,1))
                Where RetVal>=cast(GetDate() as date)
             ) B

返回

StartDate   frequency   NextDate
2016-01-02  1month      2017-02-02
2016-01-06  1month      2017-01-06
2016-03-10  3months     2017-03-10
2015-01-01  4months     2017-05-01

有兴趣的UDF

CREATE FUNCTION [dbo].[udf-Range-Date] (@R1 datetime,@R2 datetime,@Part varchar(10),@Incr int)
Returns Table
Return (
    with cte0(M)   As (Select 1+Case @Part When 'YY' then DateDiff(YY,@R1,@R2)/@Incr When 'QQ' then DateDiff(QQ,@R1,@R2)/@Incr When 'MM' then DateDiff(MM,@R1,@R2)/@Incr When 'WK' then DateDiff(WK,@R1,@R2)/@Incr When 'DD' then DateDiff(DD,@R1,@R2)/@Incr When 'HH' then DateDiff(HH,@R1,@R2)/@Incr When 'MI' then DateDiff(MI,@R1,@R2)/@Incr When 'SS' then DateDiff(SS,@R1,@R2)/@Incr End),
         cte1(N)   As (Select 1 From (Values(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) N(N)),
         cte2(N)   As (Select Top (Select M from cte0) Row_Number() over (Order By (Select NULL)) From cte1 a, cte1 b, cte1 c, cte1 d, cte1 e, cte1 f, cte1 g, cte1 h ),
         cte3(N,D) As (Select 0,@R1 Union All Select N,Case @Part When 'YY' then DateAdd(YY, N*@Incr, @R1) When 'QQ' then DateAdd(QQ, N*@Incr, @R1) When 'MM' then DateAdd(MM, N*@Incr, @R1) When 'WK' then DateAdd(WK, N*@Incr, @R1) When 'DD' then DateAdd(DD, N*@Incr, @R1) When 'HH' then DateAdd(HH, N*@Incr, @R1) When 'MI' then DateAdd(MI, N*@Incr, @R1) When 'SS' then DateAdd(SS, N*@Incr, @R1) End From cte2 )

    Select RetSeq = N+1
          ,RetVal = D 
     From  cte3,cte0 
     Where D<=@R2
)
/*
Max 100 million observations -- Date Parts YY QQ MM WK DD HH MI SS
Syntax:
Select * from [dbo].[udf-Range-Date]('2016-10-01','2020-10-01','YY',1) 
Select * from [dbo].[udf-Range-Date]('2016-01-01','2017-01-01','MM',1) 
*/