我需要使用交叉适用于得到一个值的表，每日期

Question

我有一个返回这些结果的查询：

ID  | From  | To   | Value 
------ | --------- | ---------- | ------- 
8  | 1/1/2018 | 2/28/2018 | .03 
8  | 3/1/2018 | 4/30/2018 | .04 
9  | 1/1/2018 | 1/31/2018 | .05 

我需要的是这样的：

ID  | Date  | Value   
------ | --------- | ---------- 
8  | 1/1/2018 | .03 
8  | 2/1/2018 | .03 
8  | 3/1/2018 | .04 
8  | 4/1/2018 | .04 
9  | 1/1/2018 | .05 

我有研究，它似乎像跨申请需要在这里与日期表一起使用，但不知道如何使用这个运算符。

在此先感谢！

Answer 1

一种方法是在CROSS APPLY中使用ad-hoc tally表。数字或日历表也可以做到这一点。

例

Select A.ID 
     ,B.Date 
     ,A.Value 
From YourTable A 
Cross Apply (
       Select Top (DateDiff(MONTH,A.[From],A.[To])+1) 
        Date=DateAdd(MONTH,-1+Row_Number() Over (Order By (Select Null)),A.[From]) 
       From master..spt_values n1 
      ) B 

返回

编辑 - 如果打开到UDF

我经常使用UDF来创建动态日期/时间范围。它比递归cte更快并且是参数驱动的。您提供日期/时间范围，日期部分和增量。 UDF

Select A.ID 
     ,Date = cast(B.RetVal as date) 
     ,A.Value 
From YourTable A 
Cross Apply [dbo].[udf-Range-Date](A.[From],A.[To],'MM',1) B 

的

例

的UDF如果有兴趣

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) 
*/ 

Answer 2

由于John Cappelletti提到calendar tables，并且因为我总是找借口来歌颂美德使用他们，我只是指出，如果你有一个日历表，那么解决方案很简单：

select T.id, S.date, T.value from YourTable T 
cross apply 
(
    select date from Calendar where date between T.[from] and T.[to] and day_of_month = 1 
) S order by T.id, S.date asc 

其中产量：

id  date  value 
------ ---------- ------- 
8  2018-01-01 0.03  
8  2018-02-01 0.03  
8  2018-03-01 0.04  
8  2018-04-01 0.04  
9  2018-01-01 0.05  

而这里的一切都需要建立一个日历表：

create table Calendar 
(
    id int primary key identity, 
    date datetime, 
    day_of_week as datepart(dw, date), 
    day_of_month as datepart(d, date), 
    month as datepart(m, date), 
    year as datepart(yy, date), 
    day_name as datename(dw, date) 
    --etc... 
) 

--and populate 

declare @day datetime 
set @day = '1/1/2000' 

while @day <= '12/31/2100' 
begin 

    insert Calendar select @day 
    set @day = dateadd(day, 1, @day) 

end