Re: The Practical Benefits of the Relational Model
Date: 4 Oct 2002 12:31:06 -0700
hidders_at_hcoss.uia.ac.be (Jan.Hidders) wrote in message news:<3d9d91e8$1_at_news.uia.ac.be>...
> In article <bdf69bdf.0210031023.375229d8_at_posting.google.com>,
> Mikito Harakiri <mikharakiri_at_yahoo.com> wrote:
> >It is often emphasized how beatuful relational theory is, because it
> >is based on the set theory. While there is undoubtedly some
> >connections, but may I ask why set union is a basic relational
> >operator, and intersection is not? (Intersection could be expressed
> >via combination of join and projection).
> Why do you ask questions and then put the answer right behind it in
> brackets? :-)
> -- Jan Hidders
This was not an answer. Union and intersection are dual operations in the set theory. Suddenly, this symmetry is broken in the relational theory. Received on Fri Oct 04 2002 - 21:31:06 CEST