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What is an Entity Relationship Diagram (ERD)?

ER-modeling is a data modeling technique used in software engineering to produce a conceptual data model of a information system. Diagrams created using this ER-modeling technique are called Entity-Relationship Diagrams, or ER diagrams or ERDs. So you can say that Entity Relationship Diagrams illustrate the logical structure of databases.

Dr. Peter Chen is the originator of the Entity-Relationship Model. His original paper about ER-modeling is one of the most cited papers in the computer software field. Currently the ER model serves as the foundation of many system analysis and design methodologies, computer-aided software engineering (CASE) tools, and repository systems.

The original notation for ER-Diagrams uses rectangles to represent entities, and diamonds to represent relationships. Alternative notations include:

  • Crow's Foot
  • IDEF1X

There are three basic elements in ER-Diagrams:

  • Entities are the "things" for which we want to store information. An entity is a person, place, thing or event.
  • Attributes are the data we want to collect for an entitiy.
  • Relationships describe the relations between the entities.
ERDs show entities in a database and relationships between tables within that database. It is essential to have ER-Diagrams if you want to create a good database design. The diagrams help focus on how the database actually works.

er diagram
Figure 1: ER Diagram made with DeZign for Databases.


Learn Get products and technologies
  • Make new ER Diagrams or generate ER Diagrams from existing databases with DeZign for Databases trial software, available for download directly from Datanamic's download section.