SQLServer中以星期一為每週第一天 計算週數，但是在網上搜了，看了一些，比如如下的文章：

寫的都挺複雜，一堆的sql程式碼，但是實際運行了一下，都是不對的。。。

比如下面是摘自網上的程式碼：

DECLARE @DATE DATETIME = '2012-01-29'
DECLARE @FIRST_DATE_OF_YEAR DATETIME = DATEADD(YYYY, DATEDIFF(YYYY, 0, @DATE),
                                               0) 

SELECT  DATEPART(WEEK, @DATE) , -- 一年中的週數，預設以週日開始  

        DATEADD(WK, DATEDIFF(WK, 0, @DATE), 0) , -- 當前周的週一，預設從週日開始，但是仍然找週一 

        DATEADD(DAY, -1, DATEADD(WK, DATEDIFF(WK, 0, @DATE), 0)) , -- 當前周先找週一，然後往前一天找到週日 

        DATEDIFF(DAYOFYEAR, @FIRST_DATE_OF_YEAR,
                 DATEADD(DAY, -1, DATEADD(WK, DATEDIFF(WK, 0, @DATE), 0))) , -- 當前天離年第一天的間隔 

        DATEDIFF(DAYOFYEAR, @FIRST_DATE_OF_YEAR,
                 DATEADD(DAY, -1, DATEADD(WK, DATEDIFF(WK, 0, @DATE), 0))) / 7 + 1 -- 按天計算的週數
 

SELECT GETDATE() AS THEDAY,
       case when datepart(weekday,getdate()) in (2,3,4,5,6,7) then DATEPART(WEEK,GETDATE())
            else DATEPART(WEEK,GETDATE()) -1 
  end AS WEEKS
/*
THEDAY	WEEKS
2017-03-15 10:55:12.193	11
*/

select  getdate() as today,
		case when datepart(weekday,getdate()) in (2,3,4,5,6,7) and 
				  DATEPART(WEEKday,datename(year,getdate())+'-01-01') = 1  then datepart(week,getdate()) +1
		          
			 when datepart(weekday,getdate()) =1  and  
				  DATEPART(WEEKday,datename(year,getdate())+'-01-01') = 1  then datepart(week,getdate()) 
		     
			 when datepart(weekday,getdate()) in (2,3,4,5,6,7) then datepart(week,getdate()) 
			 else datepart(week,getdate())  -1 
		end  as week 
/*
today	week
2017-03-15 10:55:53.507
*/