Generating Usage Reports

To get total reservations on all machines in minutes for certain period:

SELECT 
sum((reservations.end_date   + (reservations.endTime * 60))-(reservations.start_date + (reservations.startTime * 60)))/60 duration
FROM reservations
WHERE unix_timestamp('2000-01-01') <=(reservations.start_date + (reservations.startTime * 60))  AND
unix_timestamp('2016-03-31') >= (reservations.end_date   + (reservations.endTime * 60))
AND is_pending = 0;