Super Key in RDBMS

Super Key is an attribute (or a set of attributes) that uniquely identify a tuple i.e. an entity in entity set.

It is a superset of Candidate Key, since Candidate Keys are selected from super key.

Example

Let us see an example −

<Student>

Student_ID	Student_Enroll	Student_Name	Student_Email
S02	4545	Dave	ddd@gmail.com
S34	4541	Jack	jjj@gmail.com
S22	4555	Mark	mmm@gmail.com

The following are the super keys for the above table −

{Student_ID}
{Student_Enroll}
{Student_Email}
{Student_ID, Student_Enroll}
{Studet_ID, Student_Name}
{Student_ID, Student_Email}
{Student_Name, Student_Enroll}
{Student_ID, Student_Enroll, Student_Name}
{Student_ID, Student_Enroll, Student_Email}
{Student_ID, Student_Enroll, Student_Name, Student_Email}

The following would be the candidate key from the above −

{Student_ID}
{Student_Enroll}
{Student_Email}