GATE 2022 CS – Question 31
Consider a relation $R(A,B,C,D,E)$ with the following three functional dependencies.
$AB\to C$; $BC\to D$; $C\to E$;
The number of superkeys in the relation R is _____________.
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Correct answer: 8
Explanation
A and B appear on no right-hand side, so both are in every key, and $(AB)^+=ABCDE$ makes AB the only candidate key. Superkeys are the supersets of AB, which number $2^3=8$.