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Date: Sun, 10 Oct 2004 11:14:50 +0100
From: Paul <paul@test.com>
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Subject: Re: 4 the FAQ: Are Commercial DBMS Truly Relational?
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Laconic2 wrote:
>>You lost me. Do you mean something besides the part where
>>there are no rows on the right corresponding to rows on the
>>left, or do you mean something else?
> 
> No.  I meant that an outer join can introduce NULLS,  and NULLS don't belong
> in relations.

In a truly relational system you'd have an equivalent to the SQL OUTER 
JOIN, but it would have to specify default values for every relevant 
column in the SELECT list, so that if there wasn't a matching row, you'd 
have some non-NULL values to return.

Paul.