From: | Joshua Daniel Franklin <joshua(at)iocc(dot)com> |
---|---|
To: | pgsql-novice(at)postgresql(dot)org |
Subject: | operating on data from multiple rows? |
Date: | 2002-10-22 19:06:43 |
Message-ID: | Pine.LNX.4.44.0210221351200.29304-100000@iocc.com |
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Thread: | |
Lists: | pgsql-novice |
Here is a problem I've run into with an old IMHO poorly designed database:
There is a table ("log") that has fields
username, sessionid, loggedtime, loggeddate, accntstatus
A SELECT might return this data, for example:
bob 1035208 2002-10-11 11:32:00 Start
bob 1035208 2002-10-11 11:38:00 Stop
bob 1052072 2002-10-12 10:05:00 Start
bob 1052072 2002-10-12 10:15:00 Stop
I'm trying to get my head around a SELECT that will return
only one entry per sessionid with a duration instead of two entries for
each. If I had two separate tables for Start and Stop it would
be trivial with a join, but all I can think of is doing a
"SELECT ... WHERE accntstatus = 'Start'" and then grabbing the
sessionid and doing a separate SELECT for every record (and then the
math to get the duration). This seems like a bad idea since thousands
of records are retrived at a time.
Am I missing a better way?
--
Joshua Daniel Franklin
Network Administrator
IOCC.COM
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