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 _________
The symbol → indicates functional dependency in the context of a relational database. Which of the following options is/are TRUE?
Suppose the following functional dependencies hold on a relation U with attributes P, Q, R, S, and T :
P → QR
RS → T
Which of the following functional dependencies can be inferred from the above functional dependencies?
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?