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 | | From: | Kretschmer Andreas | | Subject: | Question about a select | | Date: | Sat, 22 Jan 2005 16:56:11 +0100 |
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 | Hi,
I have a table with this columns: machine, date and area.
Now i need a view with machine an week, calculated from date, and
sum(area), where date between CURRENT_DATE and now+N days.
Okay, this is not the problem, it works fine.
(the original table and the view is more complex)
The problem is, i need also rows for machine and week with no entrys in
the table. For this rows the sum(area) shold be NULL ore 0.
In other words: for every machine i need M rows, and M must be constant.
Regards & Thx, Andreas
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TIP 8: explain analyze is your friend
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| | From: | Harald Fuchs | | Subject: | Re: Question about a select | | Date: | 23 Jan 2005 16:37:47 +0100 |
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| In article <20050122155611.GA6592@kaufbach.delug.de>,
Kretschmer Andreas writes:
> Hi,
> I have a table with this columns: machine, date and area.
> Now i need a view with machine an week, calculated from date, and
> sum(area), where date between CURRENT_DATE and now+N days.
> Okay, this is not the problem, it works fine.
> (the original table and the view is more complex)
> The problem is, i need also rows for machine and week with no entrys in
> the table. For this rows the sum(area) shold be NULL ore 0.
> In other words: for every machine i need M rows, and M must be constant.
Week values don't automagically spring into existance when there are
no corresponding entries in your table. Use a set-returning function
for generating the week values you're interested in, and left-join
your table to the SRF.
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TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match
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