How to Calculate Time Difference Between Consecutive Records in a Table?

Calculating Time Difference Between Consecutive Records

The task is to determine the time difference between adjacent rows in a table with a StartDate column. Given a table structure, it is necessary to compute the temporal gap between each pair of sequential rows.

One approach involves a self-join on the MyTable. The following query achieves this:

SELECT A.requestid, A.starttime, (B.starttime - A.starttime) AS timedifference
FROM MyTable A INNER JOIN MyTable B ON B.requestid = (A.requestid + 1)
ORDER BY A.requestid ASC

This method successfully calculates the time difference between consecutive records. However, if the request IDs are not consecutive, the following query can be used:

SELECT A.requestid, A.starttime, (B.starttime - A.starttime) AS timedifference
FROM MyTable A CROSS JOIN MyTable B
WHERE B.requestid IN (SELECT MIN (C.requestid) FROM MyTable C WHERE C.requestid > A.requestid)
ORDER BY A.requestid ASC

By utilizing the CROSS JOIN and a subquery, this approach identifies the minimum request ID that is greater than the current request ID, allowing for the calculation of the time difference even for non-consecutive records.

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