A super key is a set of one or more attributes that, taken collectively, allows us to identify UNIQUELY an entity in the entity set. A super key may contain EXTRANEOUS attributes. If K is a super key, then so is any super set of K. A super key for which no PROPER subset is also a super key is CALLED a candidate key. It is possible that several distinct sets of attributes could serve as candidate keys. The primary key is one of the candidate keys that is chosen by the database designer as the principal means of identifying entities within an entity set.

A super key is a set of one or more attributes that, taken collectively, allows us to identify uniquely an entity in the entity set. A super key may contain extraneous attributes. If K is a super key, then so is any super set of K. A super key for which no proper subset is also a super key is called a candidate key. It is possible that several distinct sets of attributes could serve as candidate keys. The primary key is one of the candidate keys that is chosen by the database designer as the principal means of identifying entities within an entity set.