From: | Chris Bitmead <chris(at)tech(dot)com(dot)au> |
---|---|
To: | pgsql-sql(at)postgreSQL(dot)org |
Subject: | Re: [SQL] Tricky SQL (?) |
Date: | 1999-07-03 02:39:50 |
Message-ID: | 377D77F6.8DCFAFC8@tech.com.au |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-sql |
Use a temporary table.
Peter Eisentraut wrote:
>
> Let's say I have a table of credits with a customer number attached to it
> and a table of refunds with a customer number attached to it. Occasionally
> I want to go through this list and check if any customers still have
> more credits summed up than refunds.
>
> The technically correct choice for a query would be something like
>
> SELECT customer_nr, sum(amount) FROM ( SELECT customer_nr, amount FROM
> credits UNION customer_nr, -amount FROM refunds ) GROUP BY customer_nr
> HAVING sum(amount)>0;
>
> Unfortunately, this doesn't work because subselects are not allowed in the
> target list. The current solution is to read in all credits and refunds
> and have the application (some PHP, some Perl) do the summing and
> filtering. But this doesn't only seem clumsy but it creates unneccessay
> network traffic.
>
> Seemingly, this should be a common problem, like invoices vs. payments,
> assets vs. liabilities, etc. Does anyone have suggestions on how to tackle
> this? I am open to changes in the table structure, too.
>
> --
> Peter Eisentraut
> PathWay Computing, Inc.
--
Chris Bitmead
mailto:chris(at)tech(dot)com(dot)au
http://www.techphoto.org - Photography News, Stuff that Matters
From | Date | Subject | |
---|---|---|---|
Next Message | Thomas Mack | 1999-07-03 08:36:20 | Ascii null in varchars |
Previous Message | Peter Eisentraut | 1999-07-02 21:04:54 | Tricky SQL (?) |