My problem is simple: I have a table with a series of statuses and timestamps (for the sake of curiosity, these statuses indicate alarm levels) and I would like to query this table in order to get duration between two statuses.
Seems simple, but here comes the tricky part: I can´t create look-up tables, procedures and it should be as fast as possible as this table is a little monster holding over 1 billion records (no kidding!)...
The schema is drop dead simple:
[pk] Time Value
(actualy, there is a second pk but it is useless for this)
And below a real world example:
Timestamp Status 2013-1-1 00:00:00 1 2013-1-1 00:00:05 2 2013-1-1 00:00:10 2 2013-1-1 00:00:15 2 2013-1-1 00:00:20 0 2013-1-1 00:00:25 1 2013-1-1 00:00:30 2 2013-1-1 00:00:35 2 2013-1-1 00:00:40 0
The output, considering only a level 2 alarm, should be as follow should report the begin of a level 2 alarm an its end (when reach 0):
StartTime EndTime Interval 2013-1-1 00:00:05 2013-1-1 00:00:20 15 2013-1-1 00:00:30 2013-1-1 00:00:40 10
I have been trying all sorts of inner joins, but all of them lead me to an amazing Cartesian explosion. Can you guys help me figure out a way to accomplish this?
Thanks!
This has to be one of the harder questions I've seen today - thanks! I assume you can use CTEs? If so, try something like this:
;WITH Filtered
AS
(
SELECT ROW_NUMBER() OVER (ORDER BY dateField) RN, dateField, Status
FROM Test
)
SELECT F1.RN, F3.MinRN,
F1.dateField StartDate,
F2.dateField Enddate
FROM Filtered F1, Filtered F2, (
SELECT F1a.RN, MIN(F3a.RN) as MinRN
FROM Filtered F1a
JOIN Filtered F2a ON F1a.RN = F2a.RN+1 AND F1a.Status = 2 AND F2a.Status <> 2
JOIN Filtered F3a ON F1a.RN < F3a.RN AND F3a.Status <> 2
GROUP BY F1a.RN ) F3
WHERE F1.RN = F3.RN AND F2.RN = F3.MinRN
And the Fiddle. I didn't add the intervals, but I imagine you can handle that part from here.
Good luck.