Given the following question, I'd be glad if someone could help me.
Take the following relational schemes:
R(A, B , C) S(D, E, F)
where A and D attributes are the primary keys.
Assume to have an instance r of
R with n tuples
and an instance s of
S with m tuples.
Moreover, assume to have a referential integrity constraint between C and the primary key of S.
1) How many tuples does the θ-join between s and r contain if the join predicate is C = D? 2) How many tuples does the θ-join between s and r contain if the join predicate is B = E?
n tuples since it all depends on the number of records belonging to the
second relation that match the records which are part of the first one
zero since there's no common attributes
Is my reasoning correct?
Any help will be highly appreciated...thanks in advance