在sqlServer自定义一个用户定义星期函数

程序开发过程中需要做周别统计与显示报表。在做之前，得先找出所在年份周别的开始日期与结束日期。每年每周的开始与结束日期都不尽相同。为了该功能，在sql Server自定义一个用户定义星期函数

SET ANSI_NULLS ON 
GO 
SET QUOTED_IDENTIFIER ON 
GO 
ALTER FUNCTION [dbo].[udf_Week] 
( 
@StartYear INT, 
@EndYear INT 
) 
RETURNS @Week TABLE([WeekId] INT IDENTITY(1,1) PRIMARY KEY,[Year] [INT] NULL,[Week] [INT] NULL,[StartDate] [DATETIME] NULL,[EndDate] [DATETIME] NULL) 
AS 
BEGIN 
DECLARE @YearStartDate DATETIME 
DECLARE @YearEndDate DATETIME 
DECLARE @WeekStartDate DATETIME 
DECLARE @WeekEndDate DATETIME 
DECLARE @Weeks INT 

WHILE @StartYear <= @EndYear 
BEGIN 
SET @YearStartDate = CAST((CAST(@StartYear AS VARCHAR(4)) + '-01-01') AS DATETIME) 
SET @YearEndDate= CAST((CAST(@StartYear AS VARCHAR(4))+ '-12-31') AS DATETIME) 
SET @Weeks = 1 

IF DATEPART(DW,@YearStartDate) > 4 
SET @YearStartDate = DATEADD(DAY,(8 - DATEPART(DW,@YearStartDate)) ,@YearStartDate) 
ELSE 
SET @YearStartDate = DATEADD(DAY,(-(DATEPART(DW,@YearStartDate)-1)),@YearStartDate) 

SET @WeekStartDate = @YearStartDate 
SET @WeekEndDate = DATEADD(DAY,6,@WeekStartDate) 
WHILE DATEDIFF(DAY,@WeekStartDate,@YearEndDate) >= 4 
BEGIN 
INSERT INTO @Week([Year],[Week],[StartDate],[EndDate]) VALUES (@StartYear,@Weeks,@WeekStartDate,@WeekEndDate) 
SET @Weeks = @Weeks + 1 
SET @WeekStartDate = @WeekStartDate + 7 
SET @WeekEndDate = @WeekEndDate + 7 
END 
SET @StartYear = @StartYear + 1 
END 
RETURN 
END