sql某个日期是当年的第几周

CREATE function GetWeekIndexFirstDate
(
   @date datetime
)
returns int
as
begin
 

 
   declare @index int;
   declare @firstDate datetime;--当年的1月1号
   declare @firstSunday datetime;--当年的第一个周日
   declare @firstWeekSunday datetime;--当年的第一周的周日
 
   set @firstDate = convert(datetime,convert(varchar(4),Year(@date)) + "-1-1")
 
   set @firstSunday = case when datepart(dw,@firstDate)=1 then @firstDate else dateadd(dd,8-datepart(dw,@firstDate),@firstDate) end;
 
   if(@date<=@firstSunday)
      set  @index = 1;
   else
      set @index = ceiling(datediff(dd,@firstSunday,@date)/7.0)+1
 
   return @index;
end



 
 

CREATE function GetWeekIndexFirstMonday
(
   @date datetime
)
returns int
as
begin
 
 
 

 
   declare @index int;
   declare @firstDate datetime;--当年的1月1号
   declare @firstMonday datetime;--当年的第一个周一
   declare @lastYearFirstDate datetime;--上一年的1月1号
   declare @lastYearFirstMonday datetime;--上一年的第一个周一
 
   select @firstDate = convert(datetime,convert(varchar(4),Year(@date)) + "-1-1")
      , @lastYearFirstDate = convert(datetime,convert(varchar(4),datepart(yyyy,@date)-1) + "-1-1")
 
   select @firstMonday = case when datepart(dw,@firstDate)<=2 then dateadd(dd,2-datepart(dw,@firstDate) ,@firstDate)
                      else dateadd(dd,9-datepart(dw,@firstDate),@firstDate) end
      ,@lastYearFirstMonday = case when datepart(dw,@lastYearFirstDate)<=2 then dateadd(dd,2-datepart(dw,@lastYearFirstDate) ,@lastYearFirstDate)
                      else dateadd(dd,9-datepart(dw,@lastYearFirstDate),@lastYearFirstDate) end;
 



   if(@date >=@firstMonday)
      set  @index = floor(datediff(dd,@firstMonday,@date)/7.0)+1;
   else
      set @index = floor(datediff(dd,@lastYearFirstMonday,@date)/7.0)+1
 
   return @index;
end