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Date: Tue, 27 Sep 2011 03:31:51 +0200
From: Andreas <maps.on@gmx.net>
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Subject: how to calculate differences of timestamps?
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How could I calculate differences of timestamps in a log-table?

Table log ( user_id integer, login boolean, ts timestamp )

So login = true would be a login-event and login = false a logout.
Is there a way to find the matching login/logout to calculate the 
difference?

Or is there a better table "design" to do this?