Super Key in DBMS

Super Key in DBMS: The super key is a column or a set of columns in the database table, which uniquely identifies the tuple or row of the same table. It is a type of key, which is the superset of the candidate key.

We are describing this concept with the following example.

This example uses an Employee table, which contains three columns/fields/attributes. The names of these three columns in the table are Employee_ID, Employee_Name, Employee_EmailID.

Table: Employee

Now, we have to search for all the super keys present in the above table.

Following are the super keys of this employee table:  

1. { Employee_ID}

2. {Employee_EmailID}

3. { Employee_ID, Employee_EmailID }

4. { Employee_ID, Employee_Name }

5. { Employee_ID, Employee_Name, Employee_EmailID }

6. { Employee_Name, Employee_EmailID }

All the above columns or sets of columns are able to uniquely identify each row in the table Employee. So, each defined key is a super key. You can easily identify the candidate keys from the above-defined keys.

Now, we will learn about the difference between the candidate and super key.

Difference Between the Super key and Candidate Key