在sql Server自定义一个用户定义星期函数

文件：.wmv；大小：19,535kb；长度：00:26:39。
下载地址：sqlfunction_udf_week.rar
以下内容于20120105更新：
2012年刚到，开发的软件使用这个函数发现bug。2012年第一周应该是2012-01-01至2012-01-07，但此函数却把2012-01-08至2012-01-14当作第一周。

就此bug对此函数修改如下：

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