Re: does a table always need a PK?

Bob,

"Bob Badour" <bbadour_at_golden.net> kirjoitti viestissä news:BLL2b.951$Xb2.85420125_at_mantis.golden.net...
> "Heikki Tuuri" <Heikki.Tuuri_at_innodb.com> wrote in message
> news:9AE2b.79$4X.9_at_read3.inet.fi...
> > Bob,
> >
> > "Bob Badour" <bbadour_at_golden.net> kirjoitti viestissä
> > news:OYy2b.694$FE.81687684_at_mantis.golden.net...
> > > "Heikki Tuuri" <Heikki.Tuuri_at_innodb.com> wrote in message
> > ...
> > > > if I can recall, the 1970 paper is not formulated as mathematical
> axioms
> > > > either. Or is it? Do you remember?
> > >
> > > rtfm: http://www.acm.org/classics/nov95/
> >
> > it is not. I did not find mathematical axioms there. Have you studied
> > mathematics?
>
> I have studied mathematics enough to reconize that the "term relation
[used]
> in its accepted mathematical sense" is sufficiently axiomatized for most
> mathematicians. A dbms is a formal logic system, and the axioms of that
> system are actually the data in the database.

for example, there are no NULLs in a mathematical relation. Codd should explain in detail how they are modeled in the relation (the mathematical structure). Did he?

> > For example, where in the 1970 paper is the following rule formalized?
> >
> > http://www.cis.ohio-state.edu/~sgomori/570/coddsrules.html:
> >
> > "
> > 9. Logical Data Independence
> > Application programs and terminal activities remain logically unimpaired
> > when information preserving changes of any kind that theoretically
permit
> > unimpairment are made to the base tables.
> > "
>
> Once again, you ignore the formal system to complain that a rule of thumb
is
> not formal. That's quite stupid, don't you think?
>
> As it happens, the above rule of thumb goes much deeper than axioms. One
can
> construct just about any formal system. For the formal system to be
useful,
> one must use a principled design for the formal system. To design a formal
> system useful for data management, one must consider the principles of
good
> data management in the design of the formal system.
>
> The above rule of thumb is actually a guiding principle for identifying
the
> principles of good data management. It encompasses such principles as the
> separation of concerns and the value of abstraction, which overlap
somewhat
> with the principles of good software development.
>
> Some will argue that mathematics does not have to be useful for anything
but
> mathematics, and I would agree. However, mathematicians use principles
like
> closure when devising their formal systems. If one compares two arbitrary
> formal systems, one can generally identify principles distinguishing the
> systems. In fact, to a large measure this is what mathematicians do.

Now you are approaching my view. Codd's 12 rules are heuristic thoughts which can be used to guide us to build formal systems. They are not exact principles. This necessarily brings a choice of also Codd-12-relational systems.

...
> > > > "* FirstSQL/J Object/Relational DBMS "
> > > >
> > > > By the way, FirstSQL probably is not Codd-12-relational? Why do you
> > claim
> > > it
> > > > to be an 'object/relational' database then? Is it 'Lee
> > > > Fesperman -relational'?
> > >
> > > It was me who pointed out SQL is not particularly relational--not Lee.
> > > FirstSQL, of course, suffers some of the same problems all SQL dbmses
> > > suffer. Unlike MySQL, I would count FirstSQL a dbms or at least a
> > > significant subset of such a system.
> >
> > Lee's claims are grossly contradictory.
>
> Your claims are grossly contradictory, but Lee's are quite consistent.

Now you are saying grossly contradictory things. Lee claims that 'the relational model' is not vague. He claims his database is 'relational'. Since Lee believes Codd's 12 rules describe a 'relational' database, Lee's database should satisfy Codd's 12 rules. But he knows it does not.

> When other SQL vendors stop making specious claims about being relational,
I
> am sure Lee will stop too.

Is this not intellectual dishonesty?
...

Best regards,

Heikki
Innobase Oy
http://www.innodb.com
InnoDB - transactions, row level locking, and foreign keys for MySQL InnoDB Hot Backup - a hot backup tool for MySQL Received on Tue Aug 26 2003 - 18:03:10 CEST