get time difference from childs - mysql

Question

I have the following structure
----------
presences
----------
id
started
ended
user_id
---------
breaks
---------
id
presence_id
started
ended
I need to create an SQL query that returns me the following information
presence_id user_id presence_time breaks_time
where presence time is (presence.ended - presence-started) - sum of (break.ended - break.started) of all the breaks related to the presence
Is there an efficient way to get this information with an sql query?
If you know how to do it in eloquent it would be even better :D
Thank you so much!

Answer 1

http://sqlfiddle.com/#!9/650a2/3
SELECT p.id presence_id,
p.user_id,
(p.ended-p.started) presence_time ,
SUM(b.ended-b.started) breaks_time
FROM presences p
LEFT JOIN breaks b
ON p.id = b.presence_id
GROUP BY p.id
UPDATE Same query grouped by user_id:
http://sqlfiddle.com/#!9/1ce21/1
SELECT
sub_total.user_id,
SUM(sub_total.presence_time) ,
SUM(sub_total.breaks_time)
FROM (
SELECT p.id presence_id,
p.user_id,
(p.ended-p.started) presence_time ,
SUM(b.ended-b.started) breaks_time
FROM presences p
LEFT JOIN breaks b
ON p.id = b.presence_id
GROUP BY p.id) sub_total
GROUP BY sub_total.user_id

Answer 2

If your started and ended are stored as datetime or timestamp, then you can easily do the calculation and find the data in minutes.
The following example will be useful when someone taking multiple short breaks through out the working hours.
Later in the application level you can convert the minutes to hour. Here is how you can do in mysql
mysql> select * from presence ;
+------+---------------------+---------------------+---------+
| id | started | ended | user_id |
+------+---------------------+---------------------+---------+
| 1 | 2015-01-01 09:00:00 | 2015-01-01 18:00:00 | 10 |
| 2 | 2015-01-01 09:20:00 | 2015-01-01 18:04:00 | 11 |
| 3 | 2015-01-01 09:10:00 | 2015-01-01 18:30:00 | 12 |
| 4 | 2015-01-02 09:23:10 | 2015-01-02 18:10:00 | 10 |
| 5 | 2015-01-02 09:50:00 | 2015-01-02 19:00:00 | 11 |
| 6 | 2015-01-02 09:10:00 | 2015-01-02 18:36:30 | 12 |
+------+---------------------+---------------------+---------+
6 rows in set (0.00 sec)
mysql> select * from breaks ;
+------+-------------+---------------------+---------------------+
| id | presence_id | started | ended |
+------+-------------+---------------------+---------------------+
| 1 | 1 | 2015-01-01 12:00:00 | 2015-01-01 12:20:30 |
| 2 | 1 | 2015-01-01 15:46:30 | 2015-01-01 15:54:26 |
| 3 | 2 | 2015-01-01 11:26:30 | 2015-01-01 11:34:23 |
| 4 | 2 | 2015-01-01 14:06:45 | 2015-01-01 14:10:20 |
| 5 | 2 | 2015-01-01 16:01:10 | 2015-01-01 16:14:57 |
| 6 | 3 | 2015-01-01 12:11:20 | 2015-01-01 12:40:05 |
| 7 | 3 | 2015-01-01 17:01:10 | 2015-01-01 17:24:21 |
| 8 | 4 | 2015-01-02 12:50:00 | 2015-01-02 13:40:00 |
| 9 | 5 | 2015-01-02 12:20:00 | 2015-01-02 13:05:30 |
| 10 | 5 | 2015-01-02 17:03:00 | 2015-01-02 17:20:00 |
| 11 | 6 | 2015-01-02 12:16:50 | 2015-01-02 12:58:30 |
+------+-------------+---------------------+---------------------+
11 rows in set (0.00 sec)
select
p.id as presence_id,
p.user_id,
timestampdiff(minute,started,ended) - b.break_time as presence_time,
b.break_time from presence p
left join (
select
presence_id,
coalesce(sum( timestampdiff(minute,started,ended ) ),0) as break_time
from breaks
group by presence_id
)b
on b.presence_id = p.id
+-------------+---------+---------------+------------+
| presence_id | user_id | presence_time | break_time |
+-------------+---------+---------------+------------+
| 1 | 10 | 513 | 27 |
| 2 | 11 | 501 | 23 |
| 3 | 12 | 509 | 51 |
| 4 | 10 | 476 | 50 |
| 5 | 11 | 488 | 62 |
| 6 | 12 | 525 | 41 |
+-------------+---------+---------------+------------+
6 rows in set (0.00 sec)

Answer 3

Thanks to #Alex I got it working, my final query is the following (using timestamps)
SELECT *,
TIME_TO_SEC(TIMEDIFF(p.ended,p.started)) as presence_time,
sum(TIME_TO_SEC(TIMEDIFF(b.ended,b.started))) as breaks_time
FROM presences p
left join presences_breaks b on b.presence_id = p.id
group by p.id