It is feasible to design a link such as sec course from a collection of many-to-one connections. Does the many-to-one cardinality limitation of the relation get enforced by the primary and foreign key constraints? Why do you believe that?

Let W(A, B) and Q(C,D) be two relation schemas. Let r₁ and r2 be the corresponding relation instances. B is a foreign key that refers to C in r2. Assuming that all tuples in r₁ and r2 satisfy referential integrity constraints, which of the following is ALWAYS TRUE? (А) Пв (г1) - Пс (rz) =Ø (B) IIc (₂)-118 (1₁) = 0 (С) Пв (г1 ) = Пс (12) (D) Пв (r1 ) - Пс (12) +Ø OB OD OA O C

In three circumstances, the usage of a surrogate key for the primary key of a connection has been discussed.

Make a version of the hybrid merge-join method that works when both relations are not physically sorted but have a sorted secondary index on the traits to be combined.