Given a relation R(A,B,C,D), with a functional dependencies A->BC, C->D, D->B. Compute {A}+

Select one:

a. {A,B}

b. {A,B,C,D}

c. {A,B,C}

d. {A} Given a relation R(A,B,C,D) with functional dependencies A->BC, C->D, D->A. Find one key of R

Select one:

a. {A,B}

b. {A}

c. {A,B,C,D}

d. {A,B,C} Given relation R(A,B) that has 2 tuples (1, 2) and (3, 4); relation S(B, C, D) has 3 tuples (2, 5, 6), (4, 7, 8) and (9, 10, 11). The natural join of R and S has ______

Select one:

a. 1 tuple (1, 2, 10, 11)

b. 2 tuples (1, 2, 3, 4) and (5, 6, 7, 8)

c. 2 tuples (1, 2, 2, 5) and (3, 4, 4, 7)

d. 2 tuples (1, 2, 5, 6) and (3, 4, 7, 8) Consider a relation with schema R(A, B, C, D) and FD's A -> B, A -> C, C -> D. Which of the following is the {A}+ ?

Select one:

a. {A}

b. {A,B,C,D}

c. {A,B}

d. {A,B,C} https://imgur.com/3vX4PS3

Suppose that R(A,B,C) and S(B,C) are bags. R has three tuples (1,1,4), (3,4,2), (2,2,3). S has two tuples (1,4), (2,3). Which of the following is a result of a expression:

δ(γA, SUM(B)->SUMB(δ(R*S)))

(Note that: the notation * denotes for the natural join)

Select one:

a. two tuples

b. one tuples

c. the expression is invalid

d. three tuples