減去時間價值問題？

Question

使用SQL Server 2000

查詢

Select id, CONVERT(char(8), CASE WHEN DateAdd(Day, - DateDiff(Day, 0, OutTime), OutTime) > Normal_Outtime THEN Cast(Normal_Outtime AS datetime) ELSE DateAdd(Day, - DateDiff(Day, 0, OutTime), OutTime) END - CASE WHEN DateAdd(Day, - DateDiff(Day, 0, InTime), InTime) < Normal_Intime THEN Cast(Normal_Intime AS datetime) ELSE DateAdd(Day, - DateDiff(Day, 0, InTime), InTime) END - cast(totalLunchtime AS datetime), 8) ELSE '00:00:00' END AS WorkedTime 
from table 

從上面的查詢，做outtime - 銀泰 - totallunchtime

列數據類型是VARCHAR

例

Id |Intime |Outtime |totallunchtime 

001 |09:00:00 |21:00:00 |01:00:00 
002 |07:00:00 |07:30:00 |01:00:00 
003 |00:00:00 |00:00:00 |01:00:00 

WorkedTime意味着（outti我 - 銀泰 - totalLunchtime）

獲得輸出這樣

id |workedtime 

001 |11:00:00 
002 |23:30:00 
003 |23:00:00 

只有totallunchtime的問題，同時減去00:00:00它給人23:00:00，也爲PERSONID 002它給人23:30 ：00應該只給出00:30:00

預計輸出

id |workedtime 

001 |11:00:00 
002 |00:23:00 
003 |00:00:00 

...等，

需要查詢幫助

Answer 1

會這樣的工作嗎？

declare @a datetime 
declare @b datetime 
declare @c datetime 

set @a = '09:00:00' 
set @b = '17:00:00' 
set @c = '01:00:00' 

select @b - @a - case when datediff(n, @a, @b) < 60 then '00:00:00' else @c end 

如果你需要比這更多，那麼你需要在什麼條件下totallunchtime欄應考慮澄清。