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Re: Easiest way to extract owner-id from a third table

From: Thom Brown <thom(at)linux(dot)com>
To: Rikard Bosnjakovic <rikard(dot)bosnjakovic(at)gmail(dot)com>
Cc: pgsql-novice(at)postgresql(dot)org
Subject: Re: Easiest way to extract owner-id from a third table
Date: 2010-08-19 17:46:15
Message-ID: AANLkTikZMEFNHHP=tavzDHOL7Ee__mHBSuMXQwLDhu2D@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-novice
On 19 August 2010 18:40, Rikard Bosnjakovic
<rikard(dot)bosnjakovic(at)gmail(dot)com> wrote:
> I have four tables:
>
> users (id, name, ...);
> components (id, owner_id (references users), ...);
> images (id, filename);
> component_images (id, components_id (references components), images_id
> (references images));
>
> This way, I can have unlimited amount of images per component.
>
> Now I'm looking for a way to extract the owner-id (that's specified in
> the components table) and the owner name while having only the
> image_id at hand. I can ofcourse first select a row in
> component_images and - in the application - extract the value for
> components_id. Then I can use another query to find the owner id in
> the components table, which will let me have the owner id.
>
> Is there a way to achive all this without having to fiddle around in
> the application? I haven't got the faintest idea of how to specify
> this query.
>

Try this:

SELECT components.owner_id
FROM components
INNER JOIN component_images ON components.id = component_images.components_id
WHERE component_images.images_id = %
LIMIT 1

-- 
Thom Brown
Registered Linux user: #516935

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