if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[f_weekdaycount]') and xtype in (N'FN', N'IF', N'TF'))
drop function [dbo].[f_weekdaycount]
GO

/*--計算任意兩個時間之間的星期幾的次數(橫向顯示)

	本方法直接判斷 @@datefirst 做對應處理
	不受 sp_language 及 set datefirst 的影響 	

--鄒建 2004.08(引用請保留此信息)--*/

/*--調用示例
	
	select * from f_weekdaycount('2004-9-01','2004-9-02')
--*/
create function f_weekdaycount(
@dt_begin datetime,
@dt_end datetime
)returns table
as
return(
	select 跨周數
		,周一=case a
			when -1 then case when 1 between b and c then 1 else 0 end
			when  0 then case when b<=1 then 1 else 0 end
					+case when c>=1 then 1 else 0 end
			else a+case when b<=1 then 1 else 0 end
				+case when c>=1 then 1 else 0 end
			end
		,周二=case a
			when -1 then case when 2 between b and c then 1 else 0 end
			when  0 then case when b<=2 then 1 else 0 end
					+case when c>=2 then 1 else 0 end
			else a+case when b<=2 then 1 else 0 end
				+case when c>=2 then 1 else 0 end
			end
		,周三=case a
			when -1 then case when 3 between b and c then 1 else 0 end
			when  0 then case when b<=3 then 1 else 0 end
					+case when c>=3 then 1 else 0 end
			else a+case when b<=3 then 1 else 0 end
				+case when c>=3 then 1 else 0 end
			end
		,周四=case a
			when -1 then case when 4 between b and c then 1 else 0 end
			when  0 then case when b<=4 then 1 else 0 end
					+case when c>=4 then 1 else 0 end
			else a+case when b<=4 then 1 else 0 end
				+case when c>=4 then 1 else 0 end
			end
		,周五=case a
			when -1 then case when 5 between b and c then 1 else 0 end
			when  0 then case when b<=5 then 1 else 0 end
					+case when c>=5 then 1 else 0 end
			else a+case when b<=5 then 1 else 0 end
				+case when c>=5 then 1 else 0 end
			end
		,周六=case a
			when -1 then case when 6 between b and c then 1 else 0 end
			when  0 then case when b<=6 then 1 else 0 end
					+case when c>=6 then 1 else 0 end
			else a+case when b<=6 then 1 else 0 end
				+case when c>=6 then 1 else 0 end
			end
		,周日=case a
			when -1 then case when 0 between b and c then 1 else 0 end
			when  0 then case when b<=0 then 1 else 0 end
					+case when c>=0 then 1 else 0 end
			else a+case when b<=0 then 1 else 0 end
				+case when c>=0 then 1 else 0 end
			end
	from(
		select 跨周數=case when @dt_begin<@dt_end
				then (datediff(day,@dt_begin,@dt_end)+7)/7
				else (datediff(day,@dt_end,@dt_begin)+7)/7 end
			,a=case when @dt_begin<@dt_end
				then datediff(week,@dt_begin,@dt_end)-1
				else datediff(week,@dt_end,@dt_begin)-1 end
			,b=case when @dt_begin<@dt_end
				then (@@datefirst+datepart(weekday,@dt_begin)-1)%7
				else (@@datefirst+datepart(weekday,@dt_end)-1)%7 end
			,c=case when @dt_begin<@dt_end
				then (@@datefirst+datepart(weekday,@dt_end)-1)%7
				else (@@datefirst+datepart(weekday,@dt_begin)-1)%7 end)a
)
go