Re: Is this JOIN good ?

DA Morgan wrote:
> > thanks
> > Yes, assuming they are of 100% referential integrity there, 100% "Children
> > <==> Parent" relationship
> > So given this it is still
> > "impossible to know if these single relationships are sufficient to avoid a
> > Cartesian product." ?
> >
> > What additional info do you need to know to say "JOIN is complete" ?
> >
> > thanks
> > 10gR2
>
> The business rules.
>
> Constraints are intended to enforce business rules.
> The business rules are the only thing that matters.

The result of the query can only be a cartesian product if the cardinality of C is 0 or 1. If greater than 1 then the result is some proper subset of the cartesian product.

I have to agree that the question is academic unless there are some business rules at stake. By definition every (non-outer) join is some restriction of a cartesian product (assuming all tables have candidate keys). Define a "complete" join, please.

-- 
David Portas