How to calculate Time between Start and Submit in SQL? [closed] - sql

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How do I calculate time these two blocks Start and Submit?
The Activity column has Start and Submit. I need to calculate the time difference between Submit and the Start before the Submit Activity. How do we calculate that?
Thanks!
Here is the sample Table:
Sample Table

Answer 1

I took the liberty of converting your image to a usable table:
DECLARE #Activity TABLE (Activity VARCHAR(MAX), Timestamp DATETIME)
INSERT #Activity
VALUES
('Start', '5/12/21 3:30 PM'),
('Start', '5/13/21 3:31 PM'),
('Start', '5/14/21 3:33 PM'),
('Submit', '5/15/21 3:36 PM'),
('Start', '5/14/21 3:37 PM')
Without any other identifier to associate the start and submit times, I will assume that the most recent Start applies to a Submit and that other Start entries are ignored. For any given Submit, one way to select a candidate Start is with a CROSS APPLY and appropriate selection, ordering, and TOP 1 criteria. Something like:
SELECT
StartTime = ST.TimeStamp,
SubmitTime = SU.TimeStamp,
Elapsed = SU.TimeStamp - ST.TimeStamp,
ElapsedMinutes = DATEDIFF(minute, ST.TimeStamp, SU.TimeStamp)
FROM #Activity SU
CROSS APPLY (
SELECT TOP 1 *
FROM #Activity ST
WHERE ST.Activity = 'Start'
AND ST.TimeStamp <= SU.TimeStamp
ORDER BY ST.TimeStamp DESC
) ST
WHERE SU.Activity = 'Submit'
Note the last record of your data is the actual closest match using the above criteria, yielding 1439 minutes of elapsed time. If your table contains keys that better associate your start and submit times, you should adjust the above logic accordingly.
I would also recommend an index on TimeStamp for efficient lookup.