Systems Analyst: What is the difference between ER diagram and UML class diagram?

ERD — data structure only. Class Diagram — data + behavior.

ERD (Entity-Relationship Diagram):

• Entities and attributes.
• Relationships and cardinality.
• For database design.
• No behavior.

Class Diagram:

• Classes with attributes AND methods.
• Inheritance, polymorphism.
• For OO design.
• Shows behavior.

Key differences:

• ERD — data only.
• Class — data + behavior.
• ERD — relational.
• Class — OO.