Entity Relationship Diagram Example: Video Rental System


Entity relationship diagrams (ERD) are widely used in database design and systems analysis to represent systems or problem domains. This is a simple ER diagram example that shows the entities involved in a video rental system, which consists of customer, movie and producer.

Use this ERD template to get started building your own. Customize the ERD to reflect the entities of your problem. Click Use this Template to start.

What is Entity Relationship Diagram?

An entity relationship diagram gives a snapshot of how these entities relate to each other. You can use them to illustrate how data is structured in business processes, or to detail how data is stored within relational databases. ER diagrams don't necessarily show how data is manipulated, or the exact process it steps through, but how the data entities are structured and related to each other. Entities are the things we need to store data about. Relationships are sometimes referred to as cardinalities, which describes the interactions numerically - but let's simply call them relationships.

Conceptual Design vs Logical Design vs Physical Design ERD

Conceptual Design - Creating an Entity Relationship Diagram (ERD) and associated data dictionary to represent the reality and capture business data requirements

Logical Design - Transforming ERD to relational model: tables, keys (constraints), etc.

Physical Design - Creating the database and other supporting structures based on a specific DBMS

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