Re: Few confusing things about first normal form

On 23 Oct, 01:28, Sru..._at_gmail.com wrote:
> greetings
>
> I realize that the arguments you gave here basically also answered my
> first question in another thread. But with regards to my second
> question in that other thread, your argument here is also that SQL
> doesn’t allow multi valued attributes. But if we limit our discussion
> just to the theory, then multi valued attributes can exist. Thus table
> ( where ITEM column holds multiple values ) in my second question
>
> ORDER ( ORDER_ID, ITEM )
>
> is not normalized and as such the question is still valid?
>

If ITEM truly is multi-valued then ORDER is not a relation. All attributes are equally important. The fact that it has a regular scalar attribute as a key is irrelevant because if ITEM isn't one value then the operators like equality, assignment and projection can't apply in their usual sense.

I don't mean to exclude the possibility of relation-valued attributes. A relation is a value so RVA's are perfectly OK in principle.

--
David Portas