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
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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：
代码如下:
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 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