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A relationship refers to the association between two entities in an ERD. Each end of the relationship shows the degree of how the entities are related and the optionality.

The degree can be expressed as:

  • 1:1 - One-to-One relationship in an ERD
  • 1:N - One-to-many relationship in an ERD
  • N:N - Many-to-many relationship in an ERD

For example: An employee can belong to one and only one department, but a department can have many employees (1:N).

Also see[edit]

Glossary of Terms
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