Re: Is mysql a RDBMS ?

From: Bob Badour <bbadour_at_golden.net>
Date: Mon, 25 Aug 2003 13:09:17 -0400
Message-ID: <Ows2b.657$WK7.79387750_at_mantis.golden.net>


"Daniel Guntermann" <guntermann_at_earthlink.net> wrote in message news:HQh2b.2331$Jh2.1999_at_newsread4.news.pas.earthlink.net...
>
> "Bob Badour" <bbadour_at_golden.net> wrote in message
> news:YBh2b.643$9I6.77372456_at_mantis.golden.net...
> > "Daniel Guntermann" <guntermann_at_earthlink.net> wrote in message
> > news:Gmg2b.2278$Jh2.287_at_newsread4.news.pas.earthlink.net...
> > >
> > > "Bob Badour" <bbadour_at_golden.net> wrote in message
> > > news:Vj52b.593$q25.72766566_at_mantis.golden.net...
> > > > "Heikki Tuuri" <Heikki.Tuuri_at_innodb.com> wrote in message
> > > > news:0d12b.203$yu.178_at_read3.inet.fi...
> > > > > Morten,
> > > > >
> > > > > "Morten Gulbrandsen" <Morten.Gulbrandsen_at_rwth-aachen.de> kirjoitti
> > > > viestiss?
> > > > > news:60ca69db.0308210016.822e230_at_posting.google.com...
> > > > > > Hello,
> > >
> > > [...]
> > >
> > > > > >
> > > > > > From Elmasri:
> > > > > >
> > > > > > To qualify as a genuine relational DBMS,
> > > > > > a system must have at least the following properties:
> > > > > >
> > > > > > 1.) It must store data as relations such that each column is
> > > > > > independently identified by its column name and the ordering of
> rows
> > > > > > is immaterial.
> > > > >
> > > > > This holds for MySQL.
> > > >
> > > > Are you saying that the following works with MySQL?
> > > >
> > > > select somecharfield name, someintfield id
> > > > from sometable
> > > > union
> > > > select anotherintfield id, anothercharfield name
> > > > from someothertable
> > > > ;
> > > >
> > > A small nitpick, but technically the definition by Elmasri and Navathe
> > uses
> > > "store date" as part their definition. You are demonstrating an SQL
> > > expression as a means of contradiction. Trivial, I know, but still
> their
> > > definition holds until you at least find another example that would
> > indicate
> > > a base table doesn't meet the criteria given.
> >
> > Prepend "CREATE VIEW" above.
> >
> To the user, the "virtual table" would still logically have columns
> distinguishable by name.

If you can get SQL to store the relation above at all, my hat is off to you.

> Moreover, a view is not a base table - it's a
> symbol for a relational or SQL expression.

In a relational dbms, a view is just another named relation variable.

> No need to reply, as I don't see any real value in arguing this point.

Then why did you reply?

> I
> concede that the SQL standard and that the various commercial
> implementations are not perfect in attaining a pure or even decent
> representation of the relational model; though, as Mr. Tuuri points out,
> quite a few variants of the "model" have evolved

With all due respect, that is like saying there are quite a few variants of set theory or quite a few variants of first order predicate calculus. Our understanding of these may improve over time, but they do not really vary--our understanding does.

There are issues in data management for which we currently have no good theory-based solution, and these issues naturally lead to some controversy. Missing information springs to mind, of course.

There is really no controversy among relational proponents regarding the necessity of logical identity, however. Received on Mon Aug 25 2003 - 19:09:17 CEST

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