#24 What ia an ERD. Define the RED related terms, including entities, attributes, cardinalities and relationships
According to Investopedia (2020), an entity-relationship diagram (ER diagram) is a graphical representation of entities, attributes, cardinalities, and relationships in a database. Entities represent objects or concepts, attributes describe the characteristics of an entity, cardinalities describe the number of instances of each entity that can be associated with each other, and relationships describe the connection between entities.
- Entities: The main objects or concepts that the website represents. For example, for an e-commerce website, entities may include customers, products, orders, and payments.
- Attributes: Characteristics or properties of each entity. For example, for the customer entity, attributes may include name, address, email, and phone number.
- Relationships: How the entities are related to each other. For example, in an e-commerce website, a customer may have many orders, and an order may have many products.
- Cardinalities: Nature of the relationships between entities, specifically how many instances of each entity can be associated with each other. For example, a customer can have multiple orders, but each order can only belong to one customer.
Reference:
Image Free to use under the Pixabay license. No attribution required [Accessed 22/02/2023]
Investopedia 2020, Entity-Relationship Diagram, viewed 9 March 2023, https://www.investopedia.com/terms/e/entity-relationship-diagram.asp