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Date: Thu, 09 Jun 2011 15:43:24 +0200
From: Andreas <maps.on@gmx.net>
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Subject: need help with some aggregation magic
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hi,
I have a log-table that stores events of users and projects like this
( user_id integer, project_id integer, ts timestamp, event_type integer )

I need an aggregated list of worktime per user, per project, per day.

The users can switch projects during the day so I can't work this out 
with min(ts) and max(ts).

Is there a clever way to get this with SQL ?