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Asked: 2026-05-23T07:06:26+00:00

I am new to SQL, and could not find out how to make below

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I am new to SQL, and could not find out how to make below query. Surely, I am missing a quite basic expression, but I was unable to find it myself.

I have below table, used to store application log entries. Each entry has a timestamp of recording, identifier of the application that made that entry, the action the application actually performed, and a unique ID for the given session of that application instance.



item_id  item_datetime      app action  session_id

1   2011-06-20 19:01:04     a   start   23B6C531-6D38-4E47-A887-10B945B48BD9

2   2011-06-20 19:01:05     b   start   7E6D0F55-4280-46DF-A829-F6821FF028D5

3   2011-06-20 19:03:45     b   job     7E6D0F55-4280-46DF-A829-F6821FF028D5

4   2011-06-20 19:09:33     a   job     23B6C531-6D38-4E47-A887-10B945B48BD9

5   2011-06-20 19:27:00     a   quit    23B6C531-6D38-4E47-A887-10B945B48BD9

6   2011-06-20 19:50:00     c   start   12345678-1234-4321-1234-109876543210

7   2011-06-20 19:50:01     c   quit    12345678-1234-4321-1234-109876543210

8   2011-06-20 19:50:22     b   quit    7E6D0F55-4280-46DF-A829-F6821FF028D5

In this example, there are 3 different applications “a”, “b” and “c” executed simultaneously, each session overlapping the others. What I need is a list groupped by sessions, and the sessions (resulted groups) should be ordered by session start time.
For above example table, I expect below result:



item_id  item_datetime      app action  session_id

1   2011-06-20 19:01:04     a   start   23B6C531-6D38-4E47-A887-10B945B48BD9

4   2011-06-20 19:09:33     a   job     23B6C531-6D38-4E47-A887-10B945B48BD9

5   2011-06-20 19:27:00     a   quit    23B6C531-6D38-4E47-A887-10B945B48BD9


2   2011-06-20 19:01:05     b   start   7E6D0F55-4280-46DF-A829-F6821FF028D5

3   2011-06-20 19:03:45     b   job     7E6D0F55-4280-46DF-A829-F6821FF028D5

8   2011-06-20 19:50:22     b   quit    7E6D0F55-4280-46DF-A829-F6821FF028D5


6   2011-06-20 19:50:00     c   start   12345678-1234-4321-1234-109876543210

7   2011-06-20 19:50:01     c   quit    12345678-1234-4321-1234-109876543210

I tried group by with order by, but the problem is that the result’s sorting is based on the alphabetical order of the session_id’s – but this is not what I need, the sessions id’s uniqueness is what matters, their “value” does not matter.

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1 Answer

  1. Editorial Team

    You could use a subquery to find the first date a session was seen. That allows you to order sessions:

    select  yt.item_id
,       yt.item_datetime
,       yt.app
,       yt.action
,       yt.session_id
from    (
        select  session_id
        ,       min(item_datetime) as MinDate
        from    YourTable
        group by
                session_id
        ) sessions
left join
        YourTable yt
on      yt.session_id = sessions.session_id
order by
        session.MinDate
,       yt.item_datetime
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