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Re: Query plan for NOT IN

From: Guy Rouillier <guyr-ml1(at)burntmail(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: Query plan for NOT IN
Date: 2009-10-05 19:35:05
Message-ID: 4ACA4A69.3010507@burntmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
Grzegorz Jaśkiewicz wrote:
> 
> well, as a rule of thumb - unless you can't think of a default value of 
> column - don't use nulls. So using nulls as default 'idunno' - is a bad 
> practice, but everybody's opinion on that differ.

I don't understand this point of view.  The concept of null was 
introduced into the SQL vernacular by Codd and Date expressly to 
represent unknown values.

-- 
Guy Rouillier

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