[MSSQL]日期转换成所在年度第几周

-- =============================================
-- Author:		<David Gong>
-- Create date: <2013-01-11>
-- Description:	<查询指定日期所在年份第几周>
-- =============================================
ALTER Function [dbo].[WeekOfDate]
(
@Date DateTime --要转换的日期
)returns INT
as
begin
DECLARE @Year      int                       --取得年份
DECLARE @StFinanceDate    VARCHAR(10)        --年度第一天
DECLARE @StarDay  DateTime                   --年度第一天，日期类
DECLARE @DayDiff int
DECLARE @Ret int                            --返回结果

SET @Year =DATEPART(year, @Date) --取得所在年份
SET @StarDay= CAST(@Year AS varchar)+'-01-01'
SET @DayDiff= DATEDIFF(day, convert(datetime,@StarDay,120), @Date)+1

IF @DayDiff % 7=0    SET @Ret=@DayDiff/7
IF @DayDiff % 7<>0   SET @Ret=@DayDiff/7+1

Return @Ret

end