Entity Relationship Diagram Example: Notations for Traditional ERD


This is an ER diagram example that shows the typical ERD notations you can use to create an ERD. It consists of entities, columns of entities and the relationships (with different cardinality).

Use this ER diagram template to get started building your own. Customize the ER diagram to reflect the objects of your problem. Click Use this Template to start.

What is Entity Relationship Diagram?

The ERD was introduced by Chen (1976) in early 1976. An ERD can be served as the basis for databases, which store data about the problem domain, and which use, manipulate, and constrain that data. Experts in systems analysis and database design are adept at identifying user requirements and then translating them into corresponding components of the model. The entity relationship diagram is a graphical representation of a conceptual structure of a problem domain being modeled. The ERD assists the database designer in identifying the data and the rules that will be represented and used in a database.

Steps in designing an Entity-Relationship schema

  • Identify entity types (entity type vs. attribute)
  • Identify relationship types
  • Identify and associate attributes with entity and relationship types
  • Determine attribute domains
  • Determine primary key attributes for entity types
  • Associate (refined) cardinality ratio(s) with relationship types
  • Design generalization /specialization hierarchies including constraints

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