Time difference between rows - mysql

Question

In a mysql database (ver.5.7.15) I've got the following table named operation_list containing the following data: id (autoincrement integer, primary key), operation_date_time (datetime), operation (enumerated values: START,STOP), so the table looks like that:
+------+---------------------+-----------+
| id | operation_date_time | operation |
+------+---------------------+-----------+
| 1 | 2000-01-01 06:30:45 | START |
| 2 | 2000-01-01 07:45:00 | STOP |
| 3 | 2000-01-01 08:18:12 | START |
| 4 | 2000-01-01 11:23:58 | STOP |
| 5 | 2000-01-01 15:45:01 | START |
| 6 | 2000-01-01 19:01:33 | STOP |
+------+---------------------+-----------+
Now, assuming that the first row is always a START, the last ROW is always a STOP, the STOP is always placed after a START, I need to retrieve the time difference between START and STOP in seconds. Hence, I need to write an SQL that would produce the following recordset:
+------+---------------------+-----------+
| id | operation_date_time | duration |
+------+---------------------+-----------+
| 1 | 2000-01-01 06:30:45 | 4455 |
| 3 | 2000-01-01 08:78:12 | 11146 |
| 5 | 2000-01-01 15:45:01 | 11792 |
+------+---------------------+-----------+
Where 4455 is equivalent to 1 hour, 14 minutes and 15 seconds,
11146 is equivalent to 3 hours, 5 minutes and 46 seconds,
11792 is equivalent to 3 hours, 16 minutes and 32 seconds, and so on.
What's the best way to do it in a single SQL statement without creating additional tables or dedicated scripting?

Answer 1

This works IN mysql 5.X
But it is uglier as in 8.0
SELECT
MIN(id) id
,MIN(`operation_date_time`) `operation_date_time`
,MAX(diff) duration
FROM
(SELECT
id
, IF(`operation` = 'START', 0,TIME_TO_SEC(TIMEDIFF(`operation_date_time`, #datetime))) diff
,IF(`operation` = 'START', #count := #count + 1,#count := #count) groupby
,#datetime := `operation_date_time` `operation_date_time`
FROM
(SELECT * FROM timetable ORDER by `operation_date_time` ASC) t1, (SELECT #datetime := NOW()) a,
(SELECT #count := 0) b) t2
GROUP by groupby;
CREATE TABLE timetable (
`id` INTEGER,
`operation_date_time` VARCHAR(19),
`operation` VARCHAR(5)
);
INSERT INTO timetable
(`id`, `operation_date_time`, `operation`)
VALUES
('1', '2000-01-01 06:30:45', 'START'),
('2', '2000-01-01 07:45:00', 'STOP'),
('3', '2000-01-01 08:18:12', 'START'),
('4', '2000-01-01 11:23:58', 'STOP'),
('5', '2000-01-01 15:45:01', 'START'),
('6', '2000-01-01 19:01:33', 'STOP');
✓
✓
SELECT
MIN(id) id
,MIN(`operation_date_time`) `operation_date_time`
,MAX(diff) duration
FROM
(SELECT
id
, IF(`operation` = 'START', 0,TIME_TO_SEC(TIMEDIFF(`operation_date_time`, #datetime))) diff
,IF(`operation` = 'START', #count := #count + 1,#count := #count) groupby
,#datetime := `operation_date_time` `operation_date_time`
FROM
(SELECT * FROM timetable ORDER by `operation_date_time` ASC) t1, (SELECT #datetime := NOW()) a,
(SELECT #count := 0) b) t2
GROUP by groupby;
id | operation_date_time | duration
-: | :------------------ | -------:
1 | 2000-01-01 06:30:45 | 4455
3 | 2000-01-01 08:18:12 | 11146
5 | 2000-01-01 15:45:01 | 11792
db<>fiddle here

Answer 2

SELECT operation_date_time,DURATION FROM (
SELECT *,DATEDIFF(SECOND,operation_date_time,LEAD(operation_date_time)OVER(ORDER BY ID)) AS DURATION FROM PRACTICE
)A
WHERE operation='START'

Answer 3

Use window functions to get the ending time. I am going to use a cumulative conditional min:
select t.*,
timestampdiff(second, operation_date_time, stop_dt) as diff_seconds
from (select t.*,
min(case when operation = 'STOP' then operation_date_time end) over (order by operation_date_time) as stop_dt
from t
) t
where operation = 'START';
If the data really is interleaved, then you could just use lead():
select t.*,
timestampdiff(second, operation_date_time, stop_dt) as diff_seconds
from (select t.*,
lead(operation_date_time) over (order by operation_date_time) as stop_dt
from t
) t
where operation = 'START';
EDIT:
In MySQL pre-8.0:
select t.*,
timestampdiff(second, operation_date_time, stop_dt) as diff_seconds
from (select t.*,
(select min(t2.operation_date_time)
from t t2
where t2.operation = 'STOP' and
t2.operation_date_time > t.operation_date_time
) as stop_dt
from t
) t
where operation = 'START';