Entitetsrelationsmodeller

Entitetsrelationsmodeller, often abbreviated as ER-modeller, are conceptual data models used in database design. They represent the structure of data in a database by depicting entities, their attributes, and the relationships between them. An entity is a real-world object or concept about which data is stored, such as a customer, a product, or an order. Each entity has a set of attributes, which are properties that describe the entity, like customer name, product price, or order date.

Relationships define how entities are connected to each other. For example, a "places" relationship might connect a "Customer" entity to an "Order" entity, indicating that a customer places orders. Relationships can have different cardinalities, specifying the number of instances of one entity that can be related to instances of another entity. Common cardinalities include one-to-one, one-to-many, and many-to-many. ER-modeller use graphical notations, such as boxes for entities and diamonds for relationships, to visually represent these components. This graphical representation makes it easier to understand the database structure and communicate it among stakeholders. ER-modeller serve as a blueprint for database implementation, ensuring data integrity and efficient retrieval.