limited time offer

What Is The Difference Between A Super Key And The Candidate Key?

Below are the difference between Super Key and Candidate Key:

Point of Distinction Super Key Candidate Key
Basics Super Key is an attribute (or set of attributes) that is used to uniquely identifies all attributes in a relation. Candidate key is a set of attributes (or attribute) which uniquely identify the tuples in a relation or table. As we know that Primary key is a minimal super key, so there is one and only one primary key in any relation but there is more than one candidate key can take place. Candidate Key is a proper subset of a super key. A super key with no repeated attribute is called candidate key.
Relation All super keys can’t be candidate keys. But all candidate keys are super keys.
Count In a relation, Number of Super Keys are more than number of candidate key. Less than Super key
Criteria Various super keys together makes the criteria to select the candidate keys. Various candidate keys together makes the criteria to select the primary keys.

Null are allowed in both Super Key as well as Candidate Key.