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 | [email protected] |
S34 | 4541 | Jack | [email protected] |
S22 | 4555 | Mark | [email protected] |
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} |