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What is super key in DBMS?

Super key is the combination one and more attribute to uniquely identify a tuple. For example, we have a student table with attribute (stu_rollno., stu_name, stu_add, stu_branch, stu_Aadharno.)

Here we can have several sets of a superkey as given below.

stu_rollno. + stu_name
stu_rollno. + stu_name + stu_branch
stu_Aadharno. + stu_name
stu_rollno. + Stu_Aadhar
stu_Aadharno. + stu_name + stu_branch
stu_rollno. + stu_name + stu_add

These were a few combinations of superkey that can identify the tuple value obsoletely.

However, stu_rollno. and stu_Aadharno is also a candidate key which is also capable to fetch the tuple value uniquely. So stu_rollno. and stu_Aadhar will be a minimal superkey which can easily identify the whole tuple value.

See, below another example for the same.

superkey-dbms
SuperKey Example

So, here we can say that super is key is the strong combination of attributes that which provide a guarantee to provide the unique tuple value.

Super key is different from the composite key. If in a case we don’t have any candidate key in our relationship then the combination of a possible attribute which can uniquely identify a tuple value is known as a comosite key.

Conclusion:

Super key is the strong key which assures a guarantee to identify the tuple uniquely. Let’s have a relation with one candidate key with some other attributes which are not a key. Then a super key can be all possible combination of candidate key with the other attributes of the relation.

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