How to determine start/end time for events from status logs stored every 2 minutes

问题

MariaDB version: version: 10.0.38-MariaDB-0+deb8u1

I have a table where every 2 minutes is reported the status for a device (ON/OFF) with it's timestamp in unix time.

select * from devices_stats 
where device_id = 'LivingLight' 
  AND timestamp BETWEEN 1570080242 AND 1570084922;

+-------+-------------+--------+------------+-------------+
| id    | device_id   | status | timestamp  | device_iddr |
+-------+-------------+--------+------------+-------------+
| 16416 | LivingLight | OFF    | 1570080242 |           1 |
| 16427 | LivingLight | OFF    | 1570080363 |           1 |
| 16438 | LivingLight | OFF    | 1570080483 |           1 |
| 16449 | LivingLight | OFF    | 1570080602 |           1 |
| 16460 | LivingLight | OFF    | 1570080723 |           1 |
| 16471 | LivingLight | OFF    | 1570080842 |           1 |
| 16482 | LivingLight | ON     | 1570080963 |           1 |
| 16493 | LivingLight | ON     | 1570081083 |           1 |
| 16504 | LivingLight | ON     | 1570081203 |           1 |
| 16515 | LivingLight | ON     | 1570081323 |           1 |
| 16526 | LivingLight | ON     | 1570081443 |           1 |
| 16537 | LivingLight | ON     | 1570081563 |           1 |
| 16548 | LivingLight | ON     | 1570081682 |           1 |
| 16559 | LivingLight | ON     | 1570081803 |           1 |
| 16570 | LivingLight | ON     | 1570081922 |           1 |
| 16581 | LivingLight | ON     | 1570082042 |           1 |
| 16592 | LivingLight | ON     | 1570082163 |           1 |
| 16603 | LivingLight | ON     | 1570082283 |           1 |
| 16614 | LivingLight | ON     | 1570082402 |           1 |
| 16625 | LivingLight | ON     | 1570082523 |           1 |
| 16636 | LivingLight | ON     | 1570082643 |           1 |
| 16647 | LivingLight | ON     | 1570082762 |           1 |
| 16658 | LivingLight | ON     | 1570082882 |           1 |
| 16669 | LivingLight | OFF    | 1570083003 |           1 |
| 16680 | LivingLight | OFF    | 1570083123 |           1 |
| 16691 | LivingLight | OFF    | 1570083242 |           1 |
| 16702 | LivingLight | OFF    | 1570083363 |           1 |
| 16713 | LivingLight | OFF    | 1570083483 |           1 |
| 16724 | LivingLight | OFF    | 1570083603 |           1 |
| 16735 | LivingLight | OFF    | 1570083722 |           1 |
| 16746 | LivingLight | OFF    | 1570083843 |           1 |
| 16757 | LivingLight | OFF    | 1570083963 |           1 |
| 16768 | LivingLight | OFF    | 1570084083 |           1 |
| 16779 | LivingLight | OFF    | 1570084202 |           1 |
| 16790 | LivingLight | OFF    | 1570084323 |           1 |
| 16801 | LivingLight | OFF    | 1570084442 |           1 |
| 16812 | LivingLight | ON     | 1570084563 |           1 |
| 16823 | LivingLight | ON     | 1570084683 |           1 |
| 16834 | LivingLight | OFF    | 1570084803 |           1 |
| 16845 | LivingLight | OFF    | 1570084922 |           1 |
+-------+-------------+--------+------------+-------------+

I would like to retrieve a list of "ON" events with start and end time.

considering the example above i want to have an output like this:

+-------------+------------+------------+
| device_id   | start      | stop       | 
+-------------+------------+------------+
| LivingLight | 1570080963 | 1570082882 |
| LivingLight | 1570084563 | 1570084683 |

Could you please help me to create the query?

回答1:

Here is an approach using user-defined variables. It is noteworthy that even Windowing functions cannot be used in a straightforward manner in this problem. Nevertheless, your version is old, and don't support them either. Following solution is generic, and handle scenario if you dont use WHERE condition on the device_id and want multiple device_id in the result-set.

General idea here is that we compute an "island number" (denoted as chng in the query) for successive rows (based on timestamp) having same device_id and status value (either ON or OFF). Eventually, we can filter out only those island which are having ON status, and then do aggregation to get MIN() (start timestamp), and MAX() (stop timestamp).

Schema (MySQL v5.7)

CREATE TABLE device_stats
    (`id` int, `device_id` varchar(11), `status` varchar(3), `timestamp` int, `device_iddr` int)
;

INSERT INTO device_stats
    (`id`, `device_id`, `status`, `timestamp`, `device_iddr`)
VALUES
    (16416, 'LivingLight', 'OFF', 1570080242, 1),
    (16427, 'LivingLight', 'OFF', 1570080363, 1),
    (16438, 'LivingLight', 'OFF', 1570080483, 1),
    (16449, 'LivingLight', 'OFF', 1570080602, 1),
    (16460, 'LivingLight', 'OFF', 1570080723, 1),
    (16471, 'LivingLight', 'OFF', 1570080842, 1),
    (16482, 'LivingLight', 'ON', 1570080963, 1),
    (16493, 'LivingLight', 'ON', 1570081083, 1),
    (16504, 'LivingLight', 'ON', 1570081203, 1),
    (16515, 'LivingLight', 'ON', 1570081323, 1),
    (16526, 'LivingLight', 'ON', 1570081443, 1),
    (16537, 'LivingLight', 'ON', 1570081563, 1),
    (16548, 'LivingLight', 'ON', 1570081682, 1),
    (16559, 'LivingLight', 'ON', 1570081803, 1),
    (16570, 'LivingLight', 'ON', 1570081922, 1),
    (16581, 'LivingLight', 'ON', 1570082042, 1),
    (16592, 'LivingLight', 'ON', 1570082163, 1),
    (16603, 'LivingLight', 'ON', 1570082283, 1),
    (16614, 'LivingLight', 'ON', 1570082402, 1),
    (16625, 'LivingLight', 'ON', 1570082523, 1),
    (16636, 'LivingLight', 'ON', 1570082643, 1),
    (16647, 'LivingLight', 'ON', 1570082762, 1),
    (16658, 'LivingLight', 'ON', 1570082882, 1),
    (16669, 'LivingLight', 'OFF', 1570083003, 1),
    (16680, 'LivingLight', 'OFF', 1570083123, 1),
    (16691, 'LivingLight', 'OFF', 1570083242, 1),
    (16702, 'LivingLight', 'OFF', 1570083363, 1),
    (16713, 'LivingLight', 'OFF', 1570083483, 1),
    (16724, 'LivingLight', 'OFF', 1570083603, 1),
    (16735, 'LivingLight', 'OFF', 1570083722, 1),
    (16746, 'LivingLight', 'OFF', 1570083843, 1),
    (16757, 'LivingLight', 'OFF', 1570083963, 1),
    (16768, 'LivingLight', 'OFF', 1570084083, 1),
    (16779, 'LivingLight', 'OFF', 1570084202, 1),
    (16790, 'LivingLight', 'OFF', 1570084323, 1),
    (16801, 'LivingLight', 'OFF', 1570084442, 1),
    (16812, 'LivingLight', 'ON', 1570084563, 1),
    (16823, 'LivingLight', 'ON', 1570084683, 1),
    (16834, 'LivingLight', 'OFF', 1570084803, 1),
    (16845, 'LivingLight', 'OFF', 1570084922, 1)
;

Query #1

SELECT 
  device_id, MIN(timestamp) AS start, MAX(timestamp) AS stop 
FROM 
(
SELECT
  @c := IF(@s <> status OR @d <> device_id , @c+1, @c) AS chng, 
  @s := status AS status, 
  @d := device_id AS device_id, 
  timestamp
FROM 
(
  SELECT device_id, status, timestamp
  FROM device_stats 
  WHERE device_id = 'LivingLight' 
    AND timestamp BETWEEN 1570080242 AND 1570084922 
  ORDER BY device_id, timestamp
) t1
CROSS JOIN (SELECT @s := '', 
                   @d := '',
                   @c := 0) vars 
) t2 
WHERE t2.status = 'ON' 
GROUP BY device_id, chng;

| device_id   | start      | stop       |
| ----------- | ---------- | ---------- |
| LivingLight | 1570080963 | 1570082882 |
| LivingLight | 1570084563 | 1570084683 |

View on DB Fiddle

来源：https://stackoverflow.com/questions/58217219/how-to-determine-start-end-time-for-events-from-status-logs-stored-every-2-minut

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