11 Oct Entity-Relationship Diagram (ERD) in Database Management System (DBMS).
An entity-relationship diagram (ERD) is a data modeling technique that graphically illustrates an information system’s entities and the relationships between those entities. An ERD is a conceptual and representational model of data used to represent the entity framework infrastructure.
The elements of an ERD are:
Relationships Between Entities
A relationship is how the data is shared between entities. There are three types of relationships between entities:
- A one-to-one relationship (1:1). For example, if each customer in a database is associated with one mailing address.
- A one-to-many relationship (1:M). For example, a single customer might place an order for multiple products. The customer is associated with multiple entities, but all those entities have a single connection back to the same customer.
- A many-to-many relationship (M:N). For example, at a company where all call center agents work with multiple customers, each agent is associated with multiple customers, and multiple customers might also be associated with multiple agents.