3.2 Entity Types
An entity type is any type of object that we wish to store data about. Which entity types you decide to include on your diagram depends on your application. In an accounting application for a business you would store data about customers, suppliers, products, invoices and payments and if the business manufactured the products, you would need to store data about materials and production steps. Each of these would be classified as an entity type because you would want to store data about each one. In an entity-relationship diagram an entity type is shown as a box. In Fig. 3.1, CUSTOMER is an entity type. Each entity type is shown once. There may be many entity types in an entity-relationship diagram. The name of an entity type is singular since it represents a type.