How to calculate the total logged time in a day?

Question

How do I calculate the total amount number of hours spend inside in SQL? For instance, for this employee, the total amount of hours spent inside would 12-2=10.

EmpID   Enter/Exit  Time 
 2999   Entry   06:00AM 
 2999   Exit    12:00PM
 2999   Entry   01:00PM 
 2999   Exit    03:00PM 
 2999   Entry   04:00PM
 2999   Exit    06:00PM

Answer 1

In SQL Server 2008, this is painful. Assuming that the Entry/Exit values are connected and the time is really a valid date time, you can do:

select empid,
       sum(datediff(hour, t.time, t2.time)) as sum_hours
from t cross apply
     (select top (1) t2.*
      from t t2
      where t2.empid = t.empid and
            t2.enter_exit = 'exit' and
            t2.time > t.time
     ) as next_time
where t.enter_exit = 'enter'
group by empid;