question with times and intervals

Hi,

I have a table like this:

test=# select * from status_log ;
id | status | t_start | t_end
----+--------+------------------------+------------------------
1 | 1 | 2006-01-20 23:00:00+01 | 2006-01-21 06:00:00+01
1 | 1 | 2006-01-21 06:00:00+01 | 2006-01-21 22:00:00+01
1 | 2 | 2006-01-21 22:00:00+01 | 2006-01-22 05:00:00+01
1 | 1 | 2006-01-22 05:00:00+01 | 2006-01-22 15:00:00+01
1 | 2 | 2006-01-22 15:00:00+01 | 2006-01-23 02:00:00+01
(5 rows)

Now i need for a particular intervall (one day or two days, entires
days) the accumulated time for id=X and status=Y.

Exampel:

id=1, status=1, date=2006-01-21:

from 00:00:00 - 06:00:00 and
06:00:00 - 22:00:00

===> 6 hours + 16 hours = 22 hours

id=1, status=2, date=2006-01-21:
from 22:00:00 - 23:59:59

===> 2 hours

I need also this for a week or month. How can i calculate this?

Thanks very much for help.
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Andreas Kretschmer (Kontakt: siehe Header)
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