What Is Super Key In Dbms?

A superkey is a combination of attributes that can be uniquely used to identify a database record.With primary key if any other attribute is added then
that combination is called super key in other words,primary key is the minimum
possible super key.in the student table student_no+student_name is one the
super key.

If we add additional attribute to a primary key the resulting combination would still uniquely identify as instance of entity set, this augumented key are called super key
Eg. Roll no and name

A super key  is the set of one or more attribute that allow us to identify uniquely entity in an entity set.
E.g the customer_id attribute of the entity set customer is sufficient to distinguish one customer entity from another.

Explain primary and super key clearly

A column or set of columns that uniquely identifies a row within a table.

Use of the super key

A Super Key is a of attributes that collectively identify a entity in a entity set. For example, the bank account number is a super key in the bank accounts table.

From Malaysia

An attribute or a sets of attribute that uniquely identified an entity in the entity type called a  super key.

An attribute or set of attributes, that can identify uniquely in a given relation - SUPER KEY.
An attribute alone that can identify uniquely in a relation is called Primary Key.
There can be several key's in a given relation, that can be identified uniquely. Those can be called Candidate keys.

Superkey - A superkey is defined in the relational model as a set of
attributes of a relation variable (relvar) for which it holds that in
all relations assigned to that variable there are no two distinct
tuples (rows) that have the same values for the attributes in this set.
Equivalently a superkey can also be defined as a set of attributes of a
relvar upon which all attributes of the relvar are functionally
dependent.

For example, the bank account number
is a super key in the bank accounts table.


Hope It Helps

Super key is a subset of candidate key.it may be or may not be irreduceable.