Re: Few confusing things about first normal form

On 23 Oct, 01:28, Sru...@xxxxxxxxx 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
.

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