From: Aaron Bingham <bingham@cenix-bioscience.com>
To: Aaron Bono <postgresql@aranya.com>
Cc: Joost Kraaijeveld <J.Kraaijeveld@askesis.nl>
Cc: pgsql-sql@postgresql.org
Subject: Re: Can I do this smarter?
Date: Fri, 14 Jul 2006 16:07:37 +0200
Message-ID: <44B7A529.6090201@cenix-bioscience.com> (raw)
In-Reply-To: <bf05e51c0607132052l6b95d5b1m67d5620e80e7491e@mail.gmail.com>
References: <1152848488.6045.13.camel@localhost>
<bf05e51c0607132052l6b95d5b1m67d5620e80e7491e@mail.gmail.com>
Aaron Bono wrote:
> On 7/13/06, *Joost Kraaijeveld* <J.Kraaijeveld@askesis.nl
> <mailto:J.Kraaijeveld@askesis.nl>> wrote:
>
> I have three tables: customers, salesorders and invoices.
> Customers have
> salesorders and salesorders have invoices ( child tables have foreign
> key columns to their parent).
>
> I want to get a list of all invoices with their customers. This
> what I
> came up with:
>
> select
> invoices.objectid,
> invoices.invoicenumber,
> invoices.invoicedate,
> (select customer from salesorders where objectid =
> invoices.salesorderobjectid),
> (select customernumber from customers where objectid = (select
> customer from salesorders where objectid =
> invoices.salesorderobjectid)),
> (select lastname from customers where objectid = (select customer
> from salesorders where objectid = invoices.salesorderobjectid))
> from invoices
>
> Can I do this smarter as the three subselects select the same
> customer three times and I would think that 1 time is enough?
>
>
>
> SELECT
> invoices.objectid,
> invoices.invoicenumber,
> invoices.invoicedate,
> salesorders.customer,
> customers.customernumber,
> customers.lastname
> FROM invoices
> INNER JOIN salesorders ON (
> salesorders.objectid = invoices.salesorderobjectid
> )
> INNER JOIN customers ON (
> customers.objectid = salesorder.customer
> )
>
> You should do INNER and OUTER joins for connecting the tables by
> their foreign keys.
You can also rewirite this (IMO) more clearly thus:
SELECT
invoices.objectid,
invoices.invoicenumber,
invoices.invoicedate,
salesorders.customer,
customers.customernumber,
customers.lastname
FROM invoices, salesorders, customers
WHERE salesorders.objectid = invoices.salesorderobjectid
AND customers.objectid = salesorder.customer;
--
--------------------------------------------------------------------
Aaron Bingham
Senior Software Engineer
Cenix BioScience GmbH
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To: pgsql-sql@postgresql.org
Cc: bingham@cenix-bioscience.com, postgresql@aranya.com, J.Kraaijeveld@askesis.nl
Subject: Re: Can I do this smarter?
In-Reply-To: <44B7A529.6090201@cenix-bioscience.com>
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