我怎样才能得到从YYYWW在tsql的第一天

Question

有人可以帮助我得到基于年周整数像201648而不关心设置@@firstdate属性的周末的第一天和最后一天。我想在datetime格式的星期一开始iso date。

Answer 1

经过一番考虑之后，我认为我的动态日期/时间范围UDF可能对此有所帮助。我使用这个UDF来生成动态日期/时间范围。您可以提供所需的日期范围，日期部分和增量。在这种情况下，无论日期部分（WK，..）如何，我们都会按照要求获取第N个星期一。

Declare @YYYYWW int = 201648 

Select WkNbr = B.RetSeq 
     ,WkBeg = B.RetVal 
     ,WkEnd = DateAdd(DD,6,B.RetVal) 
From (
     Select MinDate=Min(RetVal) 
     From [dbo].[udf-Range-Date](DateFromParts(Left(@YYYYWW,4),1,1),DateFromParts(Left(@YYYYWW,4),1,10),'DD',1) 
     Where DateName(DW,RetVal)='Monday' 
     ) A 
Cross Apply (Select * From [dbo].[udf-Range-Date](A.MinDate,DateFromParts(Left(@YYYYWW,4),12,31),'DD',7)) B 
Where B.RetSeq = Right(@YYYYWW,2) 

返回

WkNbr WkBeg   WkEnd 
48  2016-11-28 2016-12-04 

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

declare @yrwk int = 201648 
declare @yr int = left(@yrwk,4) 
declare @wk int = right(@yrwk,2) 

select dateadd (week, @wk, dateadd (year, @yr-1900, 0)) - 4 - datepart(dw, dateadd (week, @wk, dateadd (year, @yr-1900, 0)) - 4) + 1 

--returns 11/27/2016 which is Sunday of that week (start of week) 
--change +1 to +2 at the end for "Monday"