sum up multilple datediffs of datetimes in mysql - mysql

Question

I have a table with one user and one day's worth of punches (clockin, breakout, breakin, clockout). Now say the user takes 2 or more breaks. I need to sum up the total time of all breaks taken. I have created a sqlfiddle to make it easier to show what I am trying to do. Here is my example: http://sqlfiddle.com/#!2/21542/6 Now I need to take (12:30:21 - 12:04:44) + (12:36:00 - 12:34:00) to get the total of all breaks taken. How can I do that in my query. Now pretend I have 10 users and 10 days in my table. I would need to group by day and user I know.

Answer 1

I would start by finding some way to link the punch-out records with the punch-in records from the same table. We can then put this data into a table and use it for querying against.
CREATE TEMPOARY TABLE breakPunchInOut (
SELECT
DATE(punchout.PunchDateTime) AS ShiftDate,
punchout.EmpId,
punchout.PunchId AS PunchOutID,
(SELECT
PunchId
FROM
timeclock
WHERE
timeclock.EmpId = punchout.EmpId
AND
timeclock.`In-Out` = 1
AND
timeclock.PunchDateTime > punchout.PunchDateTime
AND
DATE(timeclock.PunchDateTime) = DATE(punchout.PunchDateTime)
ORDER BY
timeclock.PunchDateTime ASC
LIMIT 1
) AS PunchInID
FROM
timeclock AS punchout
WHERE
punchout.`In-Out` = 0
HAVING
PunchInID IS NOT NULL
);
The way this query works is looking for all the "punch-outs" in a specific day, for each of these it then looks for the next "punch-in" which happened on the same day, by the same person. The HAVING clause filters out records where there is no punch-in after a punch-out - so maybe where the employee goes home for the day. This is something to remember because if someone goes home halfway through a shift then their break time will not be added to the total.
It's important to point out that this approach will only work for shifts which start and end on the same day. If you have a night shift which starts in the evening and finishes in the morning the next day, then you'll have to alter the way that you join the punch outs and punch ins together.
Now that we have this linking table, its relatively simple to use it to create a summary report for each employee and each shift:
SELECT
breakPunchInOut.ShiftDate,
breakPunchInOut.EmpId,
SUM(
TIMESTAMPDIFF(MINUTE, punchOut.PunchDateTime, punchIn.PunchDateTime)
) AS TotalBreakLengthMins
FROM
breakPunchInOut
INNER JOIN
timeclock AS punchOut
ON
punchOut.PunchId = breakPunchInOut.PunchOutId
INNER JOIN
timeclock AS punchIn
ON
punchIn.PunchId = breakPunchInOut.PunchInId
GROUP BY
breakPunchInOut.ShiftDate,
breakPunchInOut.EmpId
;
Notice we use the TIMESTAMPDIFF function, not the DATEDIFF. DATEDIFF only calculates the number of days between two dates - it's not used for time.