How to find where a total condition exist - sql

Question

I am trying to create a report that will show how long an automated sprinkler system has run for. The system is comprised of several sprinklers, with each one keeping track of only itself, and then sends that information to a database. My problem is that each sprinkler has its own run time (I.E. if 5 sprinklers all ran at the same time for 10 minutes, it would report back a total run time of 50 minutes), and I want to know only the net amount of run time - in this example, it would be 10 minutes.
The database is comprised of a time stamp and a boolean, where it records the time stamp every time a sprinkler is shut on or off (its on/off state is indicated by the 1/0 of the boolean).
So, to figure out the total net time the system was on each day - whether it was 1 sprinkler running or all of them - I need to check the database for time frames where no sprinklers were turned at all (or where ANY sprinkler at all was turned on). I would think the beginning of the query would look something like
SELECT * FROM MyTable
WHERE MyBoolean = 0
AND [ ... ]
But I'm not sure what the conditional statements that would follow the AND would be like to check the time stamps.
Is there a query I can send to the database that will report back this format of information?
EDIT:
Here's the table the data is recorded to - it's literally just a name, a boolean, and a datetime of when the boolean was changed, and that's the entire database

Answer 1

Every time a sprinkler turns on the number of running sprinklers increments by 1, and every time one turns off the number decrements by 1. If you transform the data so you get this:
timestamp on/off
07:00:05 1
07:03:10 1
07:05:45 -1
then you have a sequence of events in order; which sprinklers they refer to is irrelevant. (I've changed the zeros to -1 for reasons that will become evident in a moment. You can do this with "(2 * value) - 1")
Now put a running total together:
select a.timestamp, (SELECT SUM(a.on_off)
FROM sprinkler_events b
WHERE b.timestamp <= a.timestamp) as run_total
from sprinkler_events a
order by a.timestamp;
where sprinkler_events is the transformed data I listed above. This will give you:
timestamp run_total
07:00:05 1
07:03:10 2
07:05:45 1
and so on. Every row in this which has a run total of zeros is a time at which all sprinklers were turned off, which I think is what you're looking for. If you need to sum the time they were on or off, you'll need to do additional processing: search for "date difference between consecutive rows" and you'll see solutions for that.

Answer 2

You might consider looking for whether all the sprinklers are currently off. For example:
SELECT COUNT (DISTINCT s._NAME) AS sprinkers_currently_off
FROM (
SELECT
_NAME,
_VALUE,
_TIMESTAMP,
ROW_NUMBER() OVER (PARTITION BY _NAME ORDER BY _TIMESTAMP DESC, _VALUE) AS latest_rec
FROM sprinklers
) s
WHERE
_VALUE = 0
AND latest_rec = 1
The inner query orders the records so that you can get the latest status of all the sprinklers, and the outer query counts how many are currently off. If you have 10 sprinklers you would report them all off when this query returns 10.
You could modify this by applying a date range to the inner query if you wanted to look into the past, but this should get you on the right track.