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

--計算兩個日期相差的工作天數
CREATE FUNCTION f_WorkDay(
@dt_begin datetime,  --計算的開始日期
@dt_end  datetime    --計算的結束日期
)RETURNS int
AS
BEGIN
	DECLARE @workday int,@i int,@bz bit,@dt datetime
	IF @dt_begin>@dt_end
		SELECT @bz=1,@dt=@dt_begin,@dt_begin=@dt_end,@dt_end=@dt
	ELSE
		SET @bz=0
	SELECT @i=DATEDIFF(Day,@dt_begin,@dt_end)+1,
		@workday=@i/7*5,
		@dt_begin=DATEADD(Day,@i/7*7,@dt_begin)
	WHILE @dt_begin<=@dt_end
	BEGIN
		SELECT @workday=CASE 
			WHEN (@@DATEFIRST+DATEPART(Weekday,@dt_begin)-1)%7 BETWEEN 1 AND 5
			THEN @workday+1 ELSE @workday END,
			@dt_begin=@dt_begin+1
	END
	RETURN(CASE WHEN @bz=1 THEN -@workday ELSE @workday END)
END
GO



/*=================================================================*/

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

--在指定日期上,增加指定工作天數后的日期
CREATE FUNCTION f_WorkDayADD(
@date    datetime,  --基礎日期
@workday int       --要增加的工作日數
)RETURNS datetime
AS
BEGIN
	DECLARE @bz int
	--增加整周的天數
	SELECT @bz=CASE WHEN @workday<0 THEN -1 ELSE 1 END
		,@date=DATEADD(Week,@workday/5,@date)
		,@workday=@workday%5
	--增加不是整周的工作天數
	WHILE @workday<>0 
		SELECT @date=DATEADD(Day,@bz,@date),
			@workday=CASE WHEN (@@DATEFIRST+DATEPART(Weekday,@date)-1)%7 BETWEEN 1 AND 5
				THEN @workday-@bz ELSE @workday END
	--避免處理后的日期停留在非工作日上
	WHILE (@@DATEFIRST+DATEPART(Weekday,@date)-1)%7 in(0,6) 
		SET @date=DATEADD(Day,@bz,@date)
	RETURN(@date)
END