In the realm of Relational databases, an entity (ie an online shopper) is and must be uniquely identified by its 'primary key'. When 2 or more attributes are required to uniquely identify an entity, this collection of attributes is called a ''composite primary key''. | In the realm of Relational databases, an entity (ie an online shopper) is and must be uniquely identified by its 'primary key'. When 2 or more attributes are required to uniquely identify an entity, this collection of attributes is called a ''composite primary key''. |