Re: noobie join question

From: Oliver Elphick <olly(at)lfix(dot)co(dot)uk>
To: pgsql-general(at)postgresql(dot)org
Subject: Re: noobie join question
Date: 2015-05-11 11:16:14
Message-ID: 1431342974.3753.70.camel@linda
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On Mon, 2015-05-11 at 06:46 -0400, Steve Clark wrote:
> Hi List,
> I am having trouble trying to figure out
> how to get the result listed at the bottom.
>
> I have 3 tables units, types of units which has a description of the units,
> and a table that list associations of the units. I can't figure out
> how to do the proper joins. Any pointers would be appreciated.

SELECT us.udevice, ts.descr, ud.udevice, td.descr
FROM assoc AS a
LEFT JOIN units AS us
ON a.src_id = us.uid
LEFT JOIN types AS ts
ON us.utype = ts.id
LEFT JOIN units AS ud
ON a.dest_id = ud.uid
LEFT JOIN types AS td
ON ud.utype = td.id;

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