Re: DATA MODELLING - 3rd Normal Form

A database does not have to be in 3NF to be considered relational. From "Fundamentals of Database Systems" by Elmasri & Navathe, "A relational database usually contains many relations, with tuples in relations that are related in various ways. A relational database schema S is a set of relation schemas S={r1,r2,...,rm} and a set of integrity constraints IC." The text further goes to define IC as key constraints, entity integrity constraints (no PK can be null), and the referential integrity constraints (FK). No where in the definition does it state that that the tables must be in 3NF. In order to be relational, tables have to relate to one another. This relationship is explicitly defined by the primary, foreign key definitions. If I take a 3NF schema and decompose it for performance reasons, does my database cease to become relational? I don't think so.

My two cents.
Brian

parkstate_at_my-deja.com wrote:
>
> A database is said to be relational only if it is *at least* in third
> normal form as per relational theory.
>
> As far as advantages/disadvantages are concerned, everything depends on
> the design requirements, user requirements, the type of queries that
> will be made, etc. Unless you know what you need, you cannot say
> whether a particular design has certain advantages or disadvantages.
>
> My two cents.
> PS.
>
> In article <80c1f8$u7d$1_at_nnrp1.deja.com>,
> burkeblackman_at_my-deja.com wrote:
> > Hello, I'm curious to know what the disadvantages of modelling in 3rd
> > normal form are.
> >
> > Thanks,
> > Burke
> >
> > Sent via Deja.com http://www.deja.com/
> > Before you buy.
> >
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
Received on Fri Nov 12 1999 - 09:08:14 CST