Re: Relational Algebra Operators

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Thu, 25 Mar 1999 21:20:17 -0000
Message-ID: <922397430.16200.1.nnrp-06.9e984b29@news.demon.co.uk>

Paul Wagner wrote in message <7dc773$e36$1_at_news1.tc.umn.edu>...
> . Oracle has INTERSECT, UNION, and
MINUS
>operators which support R.A. intersect, union and difference, respectively.

Am I correct in thinking that the R.A. difference is the symmetric difference,
and therefore does not map exactly to the Oracle MINUS, and has to be emulated through a combination of set operators such as:

(A minus B) union (B minus A)
--

Jonathan Lewis
Yet another Oracle-related web site: www.jlcomp.demon.co.uk Received on Thu Mar 25 1999 - 15:20:17 CST