This SQL ER Diagram Sample contains a graphical representation of database structure and object relationships. In other words, an ER diagram is used to design and illustrate the structure of a database. The entity-relationship model (ER Model) is a high-level data model. It is made up of entities (or objects) and their relationships. Sometimes the terms ER Model and ER Diagram are used interchangeably. Many experts, however, prefer to separate them, emphasizing the conceptual nature of the ER Model, which describes the structure of data but does not explain how it is stored. ER Models deal with single entities such as Customers, whereas ER Diagrams deal with collections of commodities such as the Customers table.