Calculate the amount of time for each status - mysql

Question

I have the following table bellow.
The timeStamp is the moment that the status began.
There are some rows that don't add new information if status changed (like the second row) and they could be ignored.
I would to calculate (using mysql 5.7) the total amount of time for each status.
| timeStamp | status |
|------------------------------|
| 2019-12-10 14:00:00 | 1 |
| 2019-12-10 14:10:00 | 1 | // this row could be ignored
| 2019-12-10 14:00:00 | 2 | // more 24 hours in status 1
| 2019-12-11 14:10:00 | 2 |
| 2019-12-12 14:00:00 | 1 | // more 24 hours in status 2
| 2019-12-14 14:00:00 | 2 | // more 48 hours in status 1
| 2019-12-16 14:10:00 | 2 |
| 2019-12-17 14:20:00 | 2 |
| 2019-12-18 14:00:00 | 3 | // more 96 hours in status 2
| 2019-12-19 14:00:00 | 1 | // more 24 hours in status 3
I would like to see as result a table like bellow.
| status | amount_of_time |
|-------------------------|
| 1 | 72 hours |
| 2 | 120 hours |
| 3 | 24 hours |
What complicates this is that the status don't stay in order: is not 1, 2,3.
In the example above it is: 1, 2, 1, 2, 3, 1, so I can't use the MIN information.

Answer 1

Get the timestamp of the following row in a subquery and calculate the difference to the timestamp of the current row:
select t1.status, timestampdiff(second,
t1.timeStamp,
(
select min(t2.timeStamp)
from mytable t2
where t2.timeStamp > t1.timeStamp
)
) as diff
from mytable t1;
This will return:
| status | diff |
| ------ | ------ |
| 1 | 600 |
| 1 | 86400 |
| 2 | 600 |
| 2 | 85800 |
| 1 | 172800 |
| 2 | 173400 |
| 2 | 87000 |
| 2 | 85200 |
| 3 | 86400 |
| 1 | NULL |
View on DB Fiddle
From here it's just a matter of GROUP BY and SUM:
select status, sum(diff) as duratation_in_seconds
from (
select t1.status, timestampdiff(second,
t1.timeStamp,
(
select min(t2.timeStamp)
from mytable t2
where t2.timeStamp > t1.timeStamp
)
) as diff
from mytable t1
) x
group by status;
Result:
| status | duratation_in_seconds |
| ------ | --------------------- |
| 1 | 259800 |
| 2 | 432000 |
| 3 | 86400 |
View on DB Fiddle
If you want the time in hours, change the first line to
select status, round(sum(diff)/3600) as duratation_in_hours
and you will get:
| status | duratation_in_hours |
| ------ | ------------------- |
| 1 | 72 |
| 2 | 120 |
| 3 | 24 |
View on DB Fiddle
You might though want to use floor() instead of round(). That's not clear from your question.
In MySQL 8 you could use the LEAD() window function to get the timestamp of the next row:
select status, sum(diff) as duratation_in_seconds
from (
select
status,
timestampdiff(second, timeStamp, lead(timeStamp) over (order by timeStamp)) as diff
from mytable
) x
group by status;
View on DB Fiddle