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.