Re: DBDesign Q

"Alan" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> It is correct on an ERD, but incorrect in a relational schema.

That's a rather astounding statement. How do you propose to support your
assertion?


> "Andy" <[EMAIL PROTECTED]> wrote in message
> news:[EMAIL PROTECTED]
> > Can two entities have more than one relationship between them?
> >
> > A(A_ID PK,..., bID FK)
> >
> > B(B_ID PK,..., aID FK)
> >
> > A.bID refers to B.B_ID
> > B.aID refers to A_ID
> >
> > 2. Does it make sense?
> >
> > Product (ProductID PK, Name,., SpecialAttrID FK)
> >
> > Attribute (AttrID PK, Name,..,ProductID FK)
> >
> > Product can have many attributes. One attribute belongs to only one
> product.
> > There is only one main("special") attribute for each product
> >
> > Thank you in advance,
> > Andy
>
>