Question

Which of the following is NOT a superkey in a relational schema with attributes V, W, X, Y, Z and primary key V Y?
1. VXYZ
2. VWXZ
3. VWXY
4. VWXYZ

Answer 1

Correct Answer - Option 2 : VWXZ

Concept:

Superkey is a set of attributes within a table whose values can be used to uniquely identify a tuple. A candidate key is a minimal superkey.

Superkey is superset of candidate key or primary key.

Explanation:

Primary key is VY. (given)

All superkeys must contain this primary key VY. From the given keys, key, which doesn’t contain

the VY.

Here, option 2: VWXZ

“VWXZ” doesn’t contain the primary key VY. So, it is not a superkey.