指定周转对应日期

--例：WeekToDay(2018,18) 

--创建一个标量值函数

CREATE function [dbo].[WeekToDay](@Year int,@Week int) 
returns varchar(50)
as
begin

declare @Year1 datetime
declare @StratWeek datetime
declare @EndWeek datetime

set @Year1=convert(smalldatetime,convert(varchar(4),@Year) + '-1-1')
set @StratWeek=dateadd(day,1-datePart(weekday,@Year1),dateAdd(week,@Week-1,@Year1))
set @EndWeek=dateadd(day,6,@StratWeek)

RETURN convert(varchar(10),@StratWeek,111)

end