the relational database was invented by a mathematician named EF Codd using 'relational theory' basically applied set theory with some algebra and calculus. It was then taken an implemented by Oracle, Micosoft, IBM to build their relational databases.

So the rules are theory. Not essential to know, but its pretty decent frame of reference material. There are a ton of websites around that discuss it. The math is far more confusing than actually doing the work we do, unless your a total math geek.
>
> From: Veeraraju_Mareddi <[Email Address Removed] Date: 2003/04/30 Wed AM 07:09:07 EDT
> To: "LazyDBA.com Discussion" <[Email Address Removed] Subject: RE: codd rules
>
> What are codd rules about ?
>
> > ----------
> > From: Sami Seerangan[SMTP:[Email Address Removed] > Sent: Wednesday, April 30, 2003 3:52 PM
> > To: LazyDBA.com Discussion
> > Subject: Re: codd rules
> >
> > See
> >
> > http://members.aol.com/mbaddenda/art120.html
> > for a list of them
> >
> > I would say we satisfy (if you do not use ANY of the
> > object relational stuff)
> >
> > 1.1 The foundation rule
> > 1.2 Information rule
> > 1.3 Guaranteed access rule
> > 1.5 Dynamic catalogue rule
> > 1.6 Comprehensive data sub-language rule
> > 1.7 View updating rule ** v8 and up **
> > 1.8 High-level language rule
> > 1.9 Physical data independence rule
> > 1.10 Logical data independence rule
> > 1.11 Integrity independence rule
> > 1.12 Distribution independence rule
> > 1.13 Non-subversion rule
> >
> >
> > the one we don't is:
> >
> > 1.4 Systematic nulls rule
> > Null values are distinct from an empty character
> > string, a string of blank
> > characters, a zero or any other number, and must be
> > supported by representing
> > missing and/or inapplicable information in a
> > systematic way.
> >
> > the empty character string in general is treated as a
> > NULL in Oracle.
> >
> >
> >
> >
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