Re: Character string relation and functional dependencies

On Dec 6, 4:24 pm, Tegiri Nenashi <TegiriNena..._at_gmail.com> wrote:
> On Dec 6, 2:38 pm, Jonathan Leffler <jleff..._at_earthlink.net> wrote:
>
> > Tegiri Nenashi wrote:
> > > On Dec 6, 9:40 am, rp..._at_pcwin518.campus.tue.nl (rpost) wrote:
> > >> Another difference is that database tables are finite and variable,
>
> > > Oh, relations in database world are certainly not restricted by finite
> > > cardinality.
>
> > I thought that computers are finite, so the relations containable in
> > them are too - even if damn large. There's a big difference between
> > very large and infinite.
>
> This doesn't really matter. You can still reason about infinite
> relations with finite resources available on you computer platform.
>
> > One ultimate limitation is the uniqueness requirement. Suppose you have
> > a table with two integer columns. Since the range of the integer types
> > are finite (even if your DBMS handles multi-precision integers), then
> > the maximum number of distinct rows in the relation is also finite.
>
> All computer algebra systems work with numbers which are not
> restricted by a whim of hardware architects. 16/32/64 bit integer
> numbers (let alone floats)? give me a break!

In fact, it is quite possible to treat n-bit "integers" in an algebraically pleasant way: as the ring of integers mod 2^n.

Marshall Received on Fri Dec 07 2007 - 03:09:16 CET