if exists (select * from dbo.sysobjects where id = object_id(N'[tb_worktime]') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
drop table [tb_worktime]
GO

--定義工作時間表
CREATE TABLE tb_worktime(
	ID       int identity(1,1) PRIMARY KEY,            --序號
	time_start smalldatetime,                            --工作的開始時間
	time_end  smalldatetime,                           --工作的結束時間
	worktime  AS DATEDIFF(Minute,time_start,time_end)  --工作時數(分鐘)
)
GO

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

--計算兩個日期之間的工作時間
CREATE FUNCTION f_WorkTime(
@date_begin datetime,  --計算的開始時間
@date_end datetime     --計算的結束時間
)RETURNS int
AS
BEGIN
	DECLARE @worktime int
	IF DATEDIFF(Day,@date_begin,@date_end)=0
		SELECT @worktime=SUM(DATEDIFF(Minute,
			CASE WHEN CONVERT(VARCHAR,@date_begin,108)>time_start
				THEN CONVERT(VARCHAR,@date_begin,108)
				ELSE time_start END,
			CASE WHEN CONVERT(VARCHAR,@date_end,108)<time_end
				THEN CONVERT(VARCHAR,@date_end,108)
				ELSE time_end END))
		FROM tb_worktime 
		WHERE time_end>CONVERT(VARCHAR,@date_begin,108)
			AND time_start<CONVERT(VARCHAR,@date_end,108)
	ELSE
		SET @worktime
			=(SELECT SUM(CASE
					WHEN CONVERT(VARCHAR,@date_begin,108)>time_start
					THEN DATEDIFF(Minute,CONVERT(VARCHAR,@date_begin,108),time_end)
					ELSE worktime END)
				FROM tb_worktime 
				WHERE time_end>CONVERT(VARCHAR,@date_begin,108))
			+(SELECT SUM(CASE 
					WHEN CONVERT(VARCHAR,@date_end,108)<time_end
					THEN DATEDIFF(Minute,time_start,CONVERT(VARCHAR,@date_end,108))
					ELSE worktime END)
				FROM tb_worktime 
				WHERE time_start<CONVERT(VARCHAR,@date_end,108))
			+CASE 
				WHEN DATEDIFF(Day,@date_begin,@date_end)>1 
				THEN (DATEDIFF(Day,@date_begin,@date_end)-1)
					*(SELECT SUM(worktime) FROM tb_worktime)
				ELSE 0 END
	RETURN(@worktime)
END