I have a data from GPS tracker. Let's say something like:
CREATE TABLE IF NOT EXISTS `gps_data` (
`id` int(6) unsigned NOT NULL,
`speed` int(3) unsigned NOT NULL,
`time` varchar(200) NOT NULL,
PRIMARY KEY (`id`)
) DEFAULT CHARSET=utf8;
and some sample data:
INSERT INTO `gps_data` (`id`, `speed`, `time`) VALUES
('1', '5', '07:00'),
('2', '10', '07:10'),
('3', '0', '07:20'),
('4', '0', '07:30'),
('5', '0', '07:40'),
('6', '0', '07:50'),
('7', '20', '08:00'),
('8', '40', '08:10'),
('9', '15', '08:15'),
('10', '0', '08:32'),
('11', '0', '08:40'),
('12', '0', '08:52'),
('13', '12', '09:10'),
('14', '0', '09:25');
The question is how to find a time of first and last position with speed = 0.
So in my example I would like to have something like:
[break_start, break_stop]
[07:20, 07:50]
[08:32, 08:52]
[09:25, NULL]
Here is the Fiddle to better understanding: http://sqlfiddle.com/#!9/d79228/4
What I have started to try is:
SELECT `time` AS break_start, `time` AS break_stop FROM `gps_data` WHERE `speed`=0;
One method in MySQL is to assign a group to each row. This group can be the number of non-zero values before the row -- all rows with adjacent zero values are in the same group.
In MySQL 8+, you can use window functions for this:
select min(time), max(time)
from (select t.*,
sum(speed <> 0) over (order by time) as grp
from t
) t
where speed = 0
group by grp;
In earlier versions, one method is a correlated subquery:
select min(time), max(time)
from (select t.*,
(select count(*)
from t t2
where t2.speed <> 0 and t2.time <= t.time
) as grp
from t
) t
where speed = 0
group by grp;
Here is a SQL Fiddle.