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help / color / mirror / Atom feedFrom: Jan Ostrochovsky <ostrochovsky@mobiletech.sk>
To: David Johnston <polobo@yahoo.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: how to effectively SELECT new "customers"
Date: Sat, 1 Mar 2014 17:09:07 +0100 (CET)
Message-ID: <2042881838.607913.1393690147570.JavaMail.root@mobiletech.sk> (raw)
In-Reply-To: <1393513774376-5793882.post@n5.nabble.com>
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> Without incorporating additional meta-data about the purchases onto
> the
> customer table the most basic solution would be:
> SELECT DISTINCT customer_id FROM products WHERE date > (now() - '12
> months'::interval)
> EXCEPT
> SELECT DISTINCT customer_id FROM products WHERE date <= (now() - '12
> months'::interval)
> ---
> Another solution:
> WHERE ... >12 AND NOT EXISTS (SELECT ... WHERE <= 12)
> David J.
subsidiary matter: in what circumstances is better to use EXCEPT and in what NOT EXISTS?
are those equivalents? tried to google their comparison, but no relevant results found for PostgreSQL
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To: pgsql-sql@postgresql.org
Cc: ostrochovsky@mobiletech.sk, polobo@yahoo.com
Subject: Re: how to effectively SELECT new "customers"
In-Reply-To: <2042881838.607913.1393690147570.JavaMail.root@mobiletech.sk>
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