Re: By The Dawn's Normal Light

On Fri, 22 Oct 2004 10:04:55 +0100, Paul <paul_at_test.com> wrote:

>"A Relation is in first normal form if and only if none of the domains
>of its attributes permit compound or multivalued values *from the point
>of view of the relational engine*."
>
>Of course, a string could be viewed as a compound value by the type
>engine, which is why you get type operators like "substring" etc.

We have also list and array indexers.

>But
>from the point of view of the relational engine, a string is atomic:
>there is no way for the relational operators to break it down into
>smaller pieces.

But the relational engine has access to the type operators

select * from a where b like 'Z%';

select * from x where a[1][2] = 5;

>So this way you don't really need a definition of compound or
>multi-valued, you just need to know that to the relational engine the
>values are "black boxes" or "atoms" that can't be subdivided in any way.

This is not true, the type operators are a fundamental part of the "relational engine"

1NF is superfluous, a relation is always in 1NF

Regards Received on Fri Oct 22 2004 - 06:25:43 CDT