Question

The maximum number of superkeys for the relation schema R(E, F,G,H) with E as the key is _____

Answer 1

Concepts:

Any superset of a key (primary key or candidate key) is a superkey.

Data:

n → total number of attributes = 4

n(s) → total number of super keys

In R(E, F, G, H) E is a primary key. Therefore, it must be included in every superkey.

F, G, H may or may not included in superkey.

E   F  G  H ↓   ↓   ↓   ↓ 1   2   2   2

Formula:

Since only one superkey is present in the relation:

n(S) = 2^{n -1}

Calculation:

n(S) = 2^4-1 = 2³ = 8

Superkeys are: E, EF, EG, EH, EFG, EFH, EGH, EFGH