Re: Normalizing the ER model

Greg Boland wrote:
>
>"Jan Hidders" <hidders_at_REMOVE.THIS.uia.ua.ac.be> wrote in message
>news:3df14bce$1_at_news.uia.ac.be...
>> Greg Boland wrote:
>> >
>> >What ER modeling provides for me is migration of key/foreign key from on
>> >entity to another. But then, still, you must go through a final
>> >normalization .
>>
>> Really? Can you give an example of an ER diagram that is in some normal
>> form and for which the straightforward mapping to the relational model is
>> not in the same normal form?
>
>Wrong. Normalization applies to attributes and attributes only.

No. Not if they are not in a relation. It doesn't makes sense to say that a certain attribute is in BCNF. Such a statement can only apply to a relation or a set of relations.

>Forms 1,2,3 and BCNF are tests against relationships among attributes.

.. if these attributes are in a certain relation. And in a relationship the roles correspond with the attributes, so you can apply normalization.

>Also, there is no such thing as an ER diagram in any normal form.

Yes there is. Entities and relationships are both special cases of relations and both have attributes that can have dependencies between them. And as I already showed (and you in fact agreed with that) a fact type / relationship can be in 3NF and not in BCNF.

• Jan Hidders