Entity-Relationship Model

The ER model represents real-world data as entities and the relationships between them.

Key Concepts

• Entity: A real-world object (e.g. Student, Course).
• Attribute: Property of an entity (e.g. StudentID, Name).
• Primary Key: Uniquely identifies each entity instance.
• Relationship: Association between entities.

Cardinality

• One-to-One (1:1): One person has one passport.
• One-to-Many (1:N): One department has many employees.
• Many-to-Many (M:N): Students enrol in many courses; courses have many students.