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Re: [Gnumed-devel] Getting Canadian drug data into FreeDiams

From: Karsten Hilbert
Subject: Re: [Gnumed-devel] Getting Canadian drug data into FreeDiams
Date: Fri, 19 Feb 2010 22:40:14 +0100
User-agent: Mutt/1.5.20 (2009-06-14)

On Fri, Feb 19, 2010 at 03:12:08AM -0800, Jim Busser wrote:

> because it wants only a single record defining the drug's availability, 
> whereas Health Canada data provides a historical record of notices. 
> Accordingly there exist multiple values of
> with varying ages of records, per drug. Presumably I need to make the SELECT 
> command ignore values *except* for the newest per drug else some way to first 
> delete the non-newest records per drug.

Ah, now I understand. This is typically done with either a
GROUP BY/HAVING or a self-join.

        this_table as level1
WHERE = (select max(date) from this_table as level2 where 
level1.drug_code = level2.drug_code)
        ... other conditions ...

Does that help ?

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