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.)

Within this blog, we will explore What is the super key in DBMS? What is the primary key and super key? What is the super key and candidate key with example?….

…. What is the candidate key in DBMS, Primary key in DBMS, Super key and candidate key, Alternate key in DBMS, Candidate key in DBMS with example.

Before we go into the deep discussion for the Super key let’s see some basic questions and answers related to keys in DBMS, it will help you to understand the super key in a better manner.

What is the primary key and super key?

The primary key is a column or set of columns in a table that can identify all the details of the complete row or tuple uniquely. Whereas the Super key is a set of one or more columns that can identify the tuple value uniquely.

What is the super key and candidate key with an example?

The super key is the set of one or more columns or attributes that can identify the whole tuple or row value uniquely. Whereas the candidate key is also a set of one or more column or attribute which can identify the tuple value uniquely, but here column value or attribute value is not redundant.

A super key may or may not be a candidate key, but all the candidate keys are super key. So we can say that the super key is the superset of candidate keys.

What is an alternate key in DBMS?

A key other than a primary key is considered as the alternate key. For example in a student table we have two candidate keys like student roll no. and student phone number, if we will consider student roll no. is a primary key then in this scenario student phone number will be the alternate key of this relation.

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 that is also capable to fetch the tuple value uniquely. So stu_rollno. and stu_Aadhar will be a minimal superkey that 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.

The 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 that can uniquely identify a tuple value is known as a composite key.

Conclusion:

The 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.

Within this blog post, we have gone through What is the super key in DBMS? Where is the super key in the database? What is the primary key and super key? What is the super key and candidate key with an example? What is the candidate key in DBMS, Primary key in DBMS, Super key and candidate key, Alternate key in DBMS, Candidate key in DBMS with example

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Anurag

I am a blogger by passion, a software engineer by profession, a singer by consideration and rest of things that I do is for my destination.