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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} |
Updated on: 15-Jun-2020
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