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To: pgsql-sql@postgresql.org
From: Thomas Kellerer <spam_eater@gmx.net>
Subject: Re: mysql code questions
Date: Wed, 12 Aug 2009 20:52:33 +0200
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Ray Stell wrote on 12.08.2009 20:19:
> http://www.brentozar.com/archive/2009/04/getting-the-most-recent-record/
> How this works?  What is ttNewer?  What is a clustered primary key in mysql? 
That article talks about SQL Server not MySQL.

> select tt.*  FROM TestTable tt
>   LEFT OUTER JOIN TestTable ttNewer    
>     ON tt.id = ttNewer.id AND tt.create_date < ttNewer.create_date
>   WHERE ttNewer.id IS NULL;

I would probably do it this way:

SELECT tt. *
FROM testtable tt
WHERE create_date = (SELECT MAX(create_date)
                      FROM testtable tt2
                      WHERE tt.id = tt2.id);

Don't know which one is more efficient (with just a few rows, it doesn't really pay off to look at 
the execution plan)

Thomas