Get list with start and end values from table of datetimes

Question

Currently i have a table built up like this way

DeviceID      Timestamp            Value
----------------------------------------
Device1       1.1.2011 10:0         


        

Answer 1

Try this, though I'm not sure how well it will perform with lots of data

SELECT a.TS AS [StartTime], (SELECT TOP 1 c.TS FROM TestTime c WHERE c.TS >= a.TS AND
    NOT EXISTS(SELECT * FROM TestTime d WHERE d.TS > c.TS AND DATEDIFF(SECOND, c.TS, d.TS) <= 5) ORDER BY c.TS) AS [StopTime]
FROM TestTime a WHERE NOT EXISTS (SELECT * FROM TestTime b WHERE a.TS > b.TS AND DATEDIFF(SECOND, b.TS, a.TS) <= 5)

my table is called TestTime and the column is called TS so tweak it for your table. I've used the NOT EXISTS to check for a timestamp < the current record and within 5 seconds of it - so display if not found, i.e. a start time (or the first record in the table and then it will look for the lowest timestamp that is greater than any records found that is >= that timestamp (in case it's a single entry, so a start/stop one) and that again uses NOT EXISTS to check for a record that is greater than it and within 5 seconds - so, again, display if a record isn't found (only the 1st). You can probably tweak and improve this, but it might be a good basis.

Note that if it is still running it will list the last time found as the stop time for the last start event.

I haven't put a device name in here, for simplicity, so you would need to put that in the StopTime and WHERE clauses