An entity-relationship diagram is a data modeling technique that creates an illustration of an information system’s entities and the relationships between those entities.
As noted above, there are 3 ingredients in a standard entity-relationship diagram:
• Entities, which represent people, places, items, events, or concepts.
• Attributes, which represent properties or descriptive qualities of an entity. These are also known as data elements.
• Relationships, which represent the link between different entities.
Entities, attributes, and relationships can be represented in one of three ways: with a conceptual model, logical model, or physical model. These models increase in complexity as you move from conceptual to logical to physical. It’s usually best to start with a conceptual ERD model, so you can understand—at the highest level—the entities in your data and how they relate to each other. As you transform a conceptual ERD to a physical model, you’ll learn exactly how to implement modeled information into the database of your choice. See our Entity-relationship diagram tutorial page for more information.