Question

In my database, the times are stored as “datetimes” (I don’t know if this is the issue or not- I tried both datetime and timestamp). The structure looks like:

ID | START_DATE          | END_DATE
1  | 2011-10-10 08:15:00 | 2011-10-10 12:00:00
2  | 2011-10-11 09:00:00 | 2011-10-11 14:30:00
3  | 2011-10-12 08:45:00 | 2011-10-12 10:15:00

I am trying to get sum of total seconds between all the start and end times. Here’s what I have:

$times = mysql_query("SELECT SUM(TIMEDIFF(end_date, start_date))
AS timesum FROM schedules");

$timetotal = mysql_fetch_assoc($times);

echo $timetotal['timesum'];

Now, the sum should be 38700, but when I run the above query, it returns 100500. What’s wrong with the query?

Answer 1

You cannot sum datetime values – you need to convert to seconds first ….

SELECT SUm(time_to_sec(TIMEDIFF(end_date, start_date)))
AS timesum FROM schedules