What is a candidate key in DBMS?

An attribute or a column in a table that can identify a full tuple or row records in a data table is considered as a candidate key.

Now the question is that all the other keys like primary, alternate, super, unique, foreign also used to uniquely identify a tuple value so are they all a candidate key?

Yes, any key that is capable to identify a tuple value is considered as a candidate key though they could also have their own features like a primary key does not allow to enter a null value. Whereas unique key allows doing the same.


In a very simple language, we can say that a candidate key is a generalized concept to have unique value to identify the whole row record. thus any DBMS key fulfilling this criterion will be a candidate key.


Every key that can easily identify a tuple value with the property of uniqueness, mean to say that every tuple has a unique value for a particular attribute value is called a candidate key. There may be one and more candidate key in the database table.

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