Entity and Non-Key Areas

Publish date: 2024-05-03
Entity and Non-Key Areas

Previous Topic: Key TypesNext Topic: Primary Key Selection

Entity and Non-Key Areas

The key area contains the primary key for the entity. The primary key is a set of attributes used to identify unique instances of an entity. The primary key can be comprised of one or more primary key attributes, if the chosen attributes form a unique identifier for each instance in an entity.

An entity usually has many nonkey attributes, which appear below the horizontal line. A nonkey attribute does not uniquely identify an instance of an entity. For example, a database can have multiple instances of the same customer name, which means that “customer name” is not unique. "customer name" would probably be a nonkey attribute.

ncG1vNJzZmirY2Ourq3ZqKWar6NjsLC5jp6psKGeYsK0e7Kup6mnoql8eoGOfHhkfYKstq93o5qrmmN9pLGmuMSrYqtxW2p6hpq0aHmop5uotaa4xZh9oqSVqHyJoKyFZn6Kp567Zn6PiK2eqqaesrh7kW5rbm5hY7W1ucs%3D