This is my activities table.
activities
+----+---------+----------+-----------------+
| id | user_id | activity | log_time |
+----+---------+----------+-----------------+
| 6 | 1 | start | 12 Oct, 1000hrs |
| 2 | 1 | task | 12 Oct, 1010hrs |
| 7 | 1 | task | 12 Oct, 1040hrs |
| 3 | 1 | start | 12 Oct, 1600hrs |
| 1 | 1 | task | 12 Oct, 1610hrs |
| 9 | 1 | start | 14 Oct, 0800hrs |
| 10 | 1 | start | 16 Oct, 0900hrs |
| 4 | 1 | task | 16 Oct, 0910hrs |
| 8 | 2 | start | 12 Oct, 1000hrs |
| 5 | 2 | task | 12 Oct, 1020hrs |
+----+---------+----------+-----------------+
and I need the total time spent by the user across all sessions. Each session happens within a day and includes a 'start' and multiple 'tasks' (before the next session is initiated with a 'start'). A session duration = last task - start [the timestamp difference]
output
+---------+------------+------------------------------------------------+
| user_id | total_time | This is explanation (not a column) |
+---------+------------+------------------------------------------------+
| 1 | 60 | 12_Oct[40+10] + 14_Oct[0] + 16_Oct[10] = 60min |
| 2 | 20 | 12_Oct[20] = 20min |
+---------+------------+------------------------------------------------+
I am unable to figure out how to get the last task in a session. I have tried the basic aggregation and join queries - but it doesn't work.
As an approach, what I think I really need is to get the last column (below / session_group) somehow, and then I can aggregate and get the difference between max/min timestamp.
+----+---------+----------+-----------------+---------------+
| id | user_id | activity | log_time | session_group |
+----+---------+----------+-----------------+---------------+
| 6 | 1 | start | 12 Oct, 1000hrs | 1 |
| 2 | 1 | task | 12 Oct, 1010hrs | 1 |
| 7 | 1 | task | 12 Oct, 1040hrs | 1 |
| 3 | 1 | start | 12 Oct, 1600hrs | 2 |
| 1 | 1 | task | 12 Oct, 1610hrs | 2 |
| 9 | 1 | start | 14 Oct, 0800hrs | 3 |
| 10 | 1 | start | 16 Oct, 0900hrs | 4 |
| 4 | 1 | task | 16 Oct, 0910hrs | 4 |
| 8 | 2 | start | 12 Oct, 1000hrs | 5 |
| 5 | 2 | task | 12 Oct, 1020hrs | 5 |
+----+---------+----------+-----------------+---------------+
Please let me know if it is even possible to get the desired output via sql (MySQL) and how to go about it ? Or is it necessary to loop through the data via say Javascript ?
Below is the MySQL query for the tables:
create table activities (
id INT NOT NULL,
user_id INT NULL,
activity VARCHAR(45),
log_time DATETIME NOT NULL DEFAULT NOW(),
PRIMARY KEY(id))
ENGINE = InnoDB;
insert into activities
(id, user_id, activity, log_time)
values
(6,1,'start', '2021-10-12 10:00:00'),
(2,1,'task' , '2021-10-12 10:10:00'),
(7,1,'task' , '2021-10-12 10:40:00'),
(3,1,'start', '2021-10-12 16:00:00'),
(1,1,'task', '2021-10-12 16:10:00'),
(9,1,'task', '2021-10-14 08:00:00'),
(10,1,'start','2021-10-16 09:00:00'),
(4,1,'task', '2021-10-16 09:10:00'),
(8,2,'start', '2021-10-12 10:00:00'),
(5,2,'task', '2021-10-12 10:20:00');
You can use SUM() window function to assign a number to each session and then aggregate:
SELECT DISTINCT user_id,
SUM(TIMESTAMPDIFF(MINUTE, MIN(log_time), MAX(log_time))) OVER (PARTITION BY user_id) total_time
FROM (
SELECT *, SUM(activity = 'start') OVER (PARTITION BY user_id, DATE(log_time) ORDER BY log_time) grp
FROM activities
) t
WHERE grp > 0
GROUP BY user_id, DATE(log_time), grp;
See the demo.