Retrieve the different in hours between 2 dates

Question

I would appreciate it if someone could help me with some logic here on how to turn my timestamp function into a working payroll service.

Right now when a user logs in to my site, they can click a clock in button which timestamps the datetime format into SQL.

This is the format: 2013-05-12 09:19:00

• On click, it starts the clock in the in column.
• When they click again, it adds to the out column.

It is storing in these columns:

• id (auto_increment)
• userid (unique)
• in (datetime)
• out (datetime)

How would a function look / work to grab total hours clocked from an employee?

At the least, point me in the right direction to resolve this scenario please.

Answer 1

You can take advantage of the MySQL functions SUM and TIMESTAMPDIFF to calculate it for you:

SELECT SUM(TIMESTAMPDIFF(HOUR, `in`, `out`)) AS hours
  FROM myTable
 WHERE userid = 1

Live DEMO

Answer 2

I would select all rows with the user id, and in PHP would get function like this:

$time = 0;
while($row = $query->fetch_object())
{
    $time += (strtotime($row->out) - strtotime($row->in));
}

And then $time would be the total time which you can format in your favourite way.

Answer 3

I would use a mysql query :

select SEC_TO_TIME(SUM(TIME_TO_SEC(session_duration))) as total_session_duration
    from (
        select timediff(`in`, `out`) as session_duration 
            from employees_log #your table_name here
            where userid = [your user id]
) as t_duration

Couldn't test it, but I'm pretty sure this should work.