27. If there is a one-to-one relationship from entity A to B , then a. there exi

Question

27. If there is a one-to-one relationship from entity A to B , then
a. there exists a functional dependency from the primary key in A to the primary key in B, i.e., PK(A) -> PK(B).
b. there exists a functional dependency from the primary key in B to the primary key in A, i.e., PK(B) -> PK(A).
c. both a. and b.
d. neither a. nor b.

28. If there is a one-to-many relationship from entity A to B , then
a. there exists a functional dependency from the primary key in A to the primary key in B, i.e., PK(A) -> PK(B).
b. there exists a functional dependency from the primary key in B to the primary key in A, i.e., PK(B) -> PK(A).
c. both a. and b.
d. neither a. nor b.

29. If there is a many-to-many relationship from entity A to B , then
a. there exists a functional dependency from the primary key in A to the primary key in B, i.e., PK(A) -> PK(B).
b. there exists a functional dependency from the primary key in B to the primary key in A, i.e., PK(B) -> PK(A).
c. both a. and b.
d. neither a. nor b.

Explanation / Answer

27. OPtion c
Because any two tuples with the same value for A must have the same value for B, and any two tuples agreeing on
B must have the same value for A

28. OPtion a) many A values may have the same B value.

29. OPtion C

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