Question

Which one in the following options is not a constraint ?

• A. Primary key
• B. Unique
• C. Foreign key
• D. Candidate key

Hint:

In database design, it's important to differentiate between keys (such as candidate keys) and the constraints that are imposed to maintain data integrity (like primary and foreign keys).

Answer 1

The Correct Option is D

A constraint in a database is a rule that ensures the accuracy and integrity of data. Primary key, Unique, and Foreign key are all constraints in relational databases. A Candidate key, on the other hand, is a set of attributes that could uniquely identify a record but is not necessarily used as a constraint until selected as a primary key. Therefore, "Candidate key" is not a constraint in the sense that it does not impose a rule on the data unless it is chosen to be the primary key.