Hours difference between time in sql server

问题

I am trying to get the hours between the two dates using DATEDIFF(HOUR, FromTime, ToTime) but when the time is 00:00:00. And the I got the negative and wrong hours.

Code Below:

select FromTime, ToTime, datepart(HH, FromTime) as fromtimehours,
datepart(HH, ToTime) as totimehours, 
DATEDIFF(HOUR, FromTime, ToTime) as totalhours
from table

回答1:

How about a case statement to catch if it is a negative value and then calculate properly:

CASE WHEN DATEDIFF(HOUR, FromTime, ToTime) < 0 
THEN 24 - DATEPART(hour, FromTime) + DATEPART(hour, ToTime)
ELSE DATEDIFF(HOUR, FromTime, ToTime) 
END AS TotalHours

来源：https://stackoverflow.com/questions/25042287/hours-difference-between-time-in-sql-server