Time between SQL row state changes - sql

Question

I have a sqlite3 table that records the state of my heating system and furnce every 30 seconds. The table looks like this
TABLE CLIMATESYSTEM (
id INTEGER PRIMARY KEY AUTOINCREMENT,
Timestamp INT,
FAN INT,
SYSTEM INT
);
timestamp is the seconds since the epoch ((int)time.time) in python
a few lines of the table looks like this
5577|1452049280|1|1
5578|1452049339|1|1
5579|1452049399|1|1
5580|1452049459|1|1
5581|1452049520|0|0
5582|1452049580|0|0
5583|1452049644|1|1
5584|1452049700|1|1
5585|1452049760|1|1
5586|1452049820|0|0
what I am trying to do is count the seconds in time between when the state transition goes from on (1) to off (0) and the next transition from off to on.
example count the seconds between #5577 and #5581 -> add to TIME_SYS_ON
example count the seconds between #5581 and #5583 -> add to TIME_SYS_OFF
What I am intending on doing is to measure the total time in a 24 hour period that my heating system is running
any ideas on a starting point?
Thanks

Answer 1

First, look up the next timestamp for each row:
SELECT Timestamp,
(SELECT MIN(Timestamp)
FROM ClimateSystem AS CS2
WHERE CS2.Timestamp > ClimateSystem.Timestamp
) AS NextTimestamp,
System
FROM ClimateSystem;
Then use that to compute the length of each interval:
SELECT NextTimestamp - Timestamp,
System
FROM (SELECT Timestamp,
(SELECT MIN(Timestamp)
FROM ClimateSystem AS CS2
WHERE CS2.Timestamp > ClimateSystem.Timestamp
) AS NextTimestamp,
System
FROM ClimateSystem);
Then add filters as needed:
SELECT SUM(NextTimestamp - Timestamp),
System
FROM (SELECT Timestamp,
(SELECT MIN(Timestamp)
FROM ClimateSystem AS CS2
WHERE CS2.Timestamp > ClimateSystem.Timestamp
) AS NextTimestamp,
System
FROM ClimateSystem)
WHERE Timestamp BETWEEN :StartOfDay AND :EndOfDay
GROUP BY System;