What is an Entity-Relationship (ER) model and what are its components?

An ER model is a conceptual data model that describes the structure of a database using entities, attributes, and relationships.

Components:

Entities: Real-world objects or concepts (represented by rectangles)

• Example: Customer, Product, Order

Attributes: Properties of entities (represented by ovals)

• Example: Customer has attributes like CustomerID, Name, Email

Relationships: Associations between entities (represented by diamonds)

• Example: Customer "places" Order

Cardinality: Describes the number of instances of one entity that can be associated with another

• One-to-One (1:1): Employee has one SSN
• One-to-Many (1:M): Customer can have many Orders
• Many-to-Many (M:N): Students enrolled in Courses