How to add two time intervals?

Question

SQL Server

Good afternoon.
There is a record of working hours. People come in the morning and leave in the evening. and so the whole month. I counted the time between arrival and departure. Now I need to add up this time difference and get how much each employee was in place. How to do it?

Answer 1

From the income/departure table, use a subquery to select the employee ID and datediff (in hours) of those records whose dates belong to a certain month, and then group them by the employee ID with the main query and perform summing aggregation of hours.

select employee_id, sum(work_hours) as work_hours from (
    select employee_id, datediff(hh, coming_time, leaving_time) as work_hours
    from work_schedule
    where Year(coming_time) = Year(CURRENT_TIMESTAMP) and Month(coming_time) = Month(CURRENT_TIMESTAMP)
) as sq group by employee_id;