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Asked: 2026-05-10T21:52:21+00:00

I have a MySQL table LOGIN_LOG with fields ID, PLAYER, TIMESTAMP and ACTION. ACTION

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I have a MySQL table LOGIN_LOG with fields ID, PLAYER, TIMESTAMP and ACTION. ACTION can be either ‘login’ or ‘logout’. Only around 20% of the logins have an accompanying logout row. For those that do, I want to calculate the average duration.

I’m thinking of something like

select avg(LL2.TIMESTAMP - LL1.TIMESTAMP) from LOGIN_LOG LL1 inner join LOGIN_LOG LL2 on LL1.PLAYER = LL2.PLAYER and LL2.TIMESTAMP > LL1.TIMESTAMP left join LOGIN_LOG LL3 on LL3.PLAYER = LL1.PLAYER   and LL3.TIMESTAMP between LL1.TIMESTAMP + 1 and LL2.TIMESTAMP - 1   and LL3.ACTION = 'login' where LL1.ACTION = 'login' and LL2.ACTION = 'logout' and isnull(LL3.ID)

is this the best way to do it, or is there one more efficient?

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1 Answer

  1. Given the data you have, there probably isn’t anything much faster you can do because you have to look at a LOGIN and a LOGOUT record, and ensure there is no other LOGIN (or LOGOUT?) record for the same user between the two.

    Alternatively, find a way to ensure that a disconnect records a logout, so that the data is complete (instead of 20% complete). However, the query probably still has to ensure that the criteria are all met, so it won’t help the query all that much.

    If you can get the data into a format where the LOGIN and corresponding LOGOUT times are both in the same record, then you can simplify the query immensely. I’m not clear if the SessionManager does that for you.

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