If all you want is the sum of the last 30 then just don't use the group by.
hth,
- Stuart
P.S. Sorry about format change caused by disclaimer adder
> -----Original Message-----
> From: Castle, Lindsay [mailto:lindsay.castle@eds.com]
> Sent: 30 July 2003 05:01
> To: pgsql-general@postgresql.org
> Subject: [GENERAL] SQL SUM query limited by dates
>
> Hi All,
>
> A quick select query I'm having some dramas with;
>
> I'm trying to SUM a number of values based on them being the
> latest entries
> based on their date.
>
> Eg I have a table with element (text), date (date) and volume
> (numeric), it
> has 100 entries, I want to grab 30 entries with the most
> recent dates and
> total up the volume information.
>
> I thought something along the lines of:
> SELECT SUM(volume) from <tablename>
> WHERE element = 'name1'
> GROUP BY date
> ORDER BY date DESC LIMIT 30
>
> Of course (I believe) this will only sum up anything that has matching
> dates.
>
> Can I do this within a SELECT SUM() statement or do I need to look at
> aggregate functions?
> Or perhaps the HAVING clause could be of use for this one?
>
> My dataset has one row per date and could possibly be out of
> date order,
> hence the order by being a requirement (unless there is another way to
> ensure only the most recent dates are accounted for).
>
> Thanks in advance,
>
> Linz
>
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