Question

I have a access log, which records usernames and a timestamp at various points in the application. I want to see if I can approximate the amount of time they are spending in the application. Basically I want to join each record to the last access record based on the timestamp, so I can figure out the time difference.

I can’t think of how to join to the first record whose timestamp is less than the current record. What is the way to do this?

Answer 1

Try something like this:

SELECT A.UserName, A.EntryDate, DATEDIFF(ss,A.EntryDate, B.EntryDate) SecondsDuration
FROM YourTable A
OUTER APPLY (SELECT MAX(EntryDate) EntryDate
             FROM YourTable
             WHERE UserName = A.UserName AND EntryDate < A.EntryDate) B