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From: jack@cca.CCA.COM (Jack Orenstein)
Newsgroups: comp.databases
Subject: Re: Outer join in SQL
Message-ID: <21927@cca.CCA.COM>
Date: Tue, 24-Nov-87 09:24:19 EST
Article-I.D.: cca.21927
Posted: Tue Nov 24 09:24:19 1987
Date-Received: Fri, 27-Nov-87 21:48:46 EST
References: <1804@cognos.UUCP> <25882UH2@PSUVM>
Reply-To: jack@CCA.CCA.COM.UUCP (Jack Orenstein)
Organization: Computer Corp. of America, Cambridge, MA
Lines: 26

In article <25882UH2@PSUVM> UH2@PSUVM.BITNET (Lee Sailer) writes:
>RBASE seems to have lots of the important parts, but Oh My do they ever
>organize things in bizarre ways.

about the following:

> [1. and 2. omitted]
>
>3.  The INTERSECTION command---ah, yes---is (1) an Intersection if
>both relations (tables) have identical columns, or (2) a natural join
>otherwise.
>     
>4.  The UNION command is a relational Union if the tables have identical
>columns, or an Outer Join otherwise.

There is nothing bizarre about this (although 1 and 2 did sound odd).
A natural join is exactly an intersection when the relations have
identical columns. Same for (full) outer join and union. This isn't
just a convenient overloading of operators - it's what you get as a result
of the semantics of natural join and outer join.


Jack Orenstein


This is not a disclaimer.