Question

What is the function of the unique constraint?

(a) It ensures that no two values under an attribute are identical

(b) It ensures that all the attributes are perfectly unique in their data type

(c) It ensures that all the relations in the database have a unique set of attributes

(d) It does not have any function in SQL

I got this question in an international level competition.

The doubt is from Integrity Constraints in chapter Intermediate and Advanced Sql of RDBMS

Answer 1

The correct option is (a) It ensures that no two values under an attribute are identical

Explanation: The purpose of the unique clause is to ensure that no two values under the same attribute are identical. Primary keys are unique by default.