A Database ER Diagram is an important tool for database designers and developers who are responsible for creating and maintaining complex databases. Here is an example. It displays the structure and relationships between different entities involved in the online shopping system. Entities like customer, products, shopping cart are represented as rectangles, and attributes are represented as circles around the entity rectangles. This kind of diagram helps to provide a clear and accurate representation of the database structure, facilitating communication among stakeholders and ensuring that the final product meets the needs and expectations of users.