Business Analyst: What is an ERD relationship cardinality?

Cardinality — number of instances in relationship.

Types:

• One-to-One (1:1) — one instance each.
• One-to-Many (1:N) — one to multiple.
• Many-to-Many (M:N) — multiple to multiple.

Examples:

Notation:

• Crow's foot notation.
• Chen notation.

BA relevance:

• Define data requirements.
• Validate business rules.
• Support database design.