From: justin <justin@emproshunts.com>
To: David W Noon <dwnoon@ntlworld.com>
To: pgsql-sql@postgresql.org
Subject: Re: simple (?) join
Date: Sat, 26 Sep 2009 16:15:37 -0400
Message-ID: <4ABE7669.50001@emproshunts.com> (raw)
In-Reply-To: <20090926205349.5fa284f1@dwnoon.ntlworld.com>
References: <200909241616.36933.gary.stainburn@ringways.co.uk>
<20090924194629.44bc236f@dwnoon.ntlworld.com>
<4ABBD34B.9080600@emproshunts.com>
<20090924222106.23a5c1f3@dwnoon.ntlworld.com>
<4ABE6360.20205@emproshunts.com>
<20090926205349.5fa284f1@dwnoon.ntlworld.com>
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David W Noon wrote:
<blockquote cite="mid:20090926205349.5fa284f1@dwnoon.ntlworld.com"
type="cite">
<pre wrap="">On Sat, 26 Sep 2009 14:54:24 -0400, justin wrote about Re: [SQL] simple
(?) join:
[snip]
</pre>
<blockquote type="cite">
<pre wrap="">Quoting Gary
"How can I select all from orders and the last (latest) entry from the
orders_log?"
</pre>
</blockquote>
<pre wrap=""><!---->
In that case, a simple Cartesian product will do:
SELECT o.*, maxi.ts
FROM orders AS o,
(SELECT MAX(ol_timestamp) AS ts FROM orders_log) AS maxi;
Since the cardinality of the subquery "maxi" is 1, it will give a result
set with cardinality of the complete orders table.
I don't understand why anybody would want to do that. [De gustibus ... ]
</pre>
</blockquote>
<br>
Guessing here <br>
<br>
Answer to return the last time someone either viewed or edited the
order.<br>
<br>
This is a very common audit requirement to track who what, when and why
something happened. <br>
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To: pgsql-sql@postgresql.org
Cc: justin@emproshunts.com, dwnoon@ntlworld.com
Subject: Re: simple (?) join
In-Reply-To: <4ABE7669.50001@emproshunts.com>
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