1
GATE CSE 2024 Set 2
Numerical
+2
-0.66

A functional dependency $F: X \to Y$ is termed as a useful functional dependency if and only if it satisfies all the following three conditions:

• $X$ is not the empty set.
• $Y$ is not the empty set.
• Intersection of $X$ and $Y$ is the empty set.

For a relation $R$ with 4 attributes, the total number of possible useful functional dependencies is _________

2
GATE CSE 2024 Set 1
MCQ (More than One Correct Answer)
+2
-0.66

The symbol → indicates functional dependency in the context of a relational database. Which of the following options is/are TRUE?

A

(X, Y) → (Z, W) implies X → (Z, W)

B

(X, Y) → (Z, W) implies (X, Y) → Z

C

((X, Y) → Z and W → Y) implies (X, W) → Z

D

(X → Y and Y → Z) implies X → Z

3
GATE CSE 2021 Set 1
+2
-0.67

Consider the relation R(P, Q, S, T, X, Y, Z, W) with the following functional dependencies.

PQ → X; P → YX; Q → Y; Y → ZW

Consider the decomposition of the relation R into the constituent relations according to the following two decomposition schemes.

D1 : R = [(P, Q, S, T); (P, T, X); (Q, Y); (Y, Z, W)]

D2 : R = [(P, Q, S); (T, X); (Q, Y); (Y, Z, W)]

Which one of the following options is correct?

A

D1 is a lossy decomposition, but D2 is a lossless decomposition.

B
Both D1 and D2 are lossless decompositions.
C
Both D1 and D2 are lossy decompositions.
D
D1 is a lossless decomposition, but D2 is a lossy decomposition.
4
GATE CSE 2020
+2
-0.67
Consider a relational table R that is in 3NF, but not in BCNF. Which one of the following statements is TRUE?
A
A cell in R holds a set instead of an atomic value.
B
R has a nontrivial functional dependency X $$\to$$ A, where X is not a superkey and A is a non-prime attribute and X is not a proper subset of any key
C
R has a nontrivial functional dependency X $$\to$$ A, where X is not a superkey and A is a non-prime attribute and X is a proper subset of some key.
D
R has a nontrivial functional dependency X $$\to$$ A, where X is not a superkey and A is a prime attribute.
GATE CSE Subjects
EXAM MAP
Medical
NEET