Relationship Types

Relationship types represent meaningful associations between entities. The degree of a relationship refers to the number of participating entities:

• Unary: A single entity type involved.
• Binary: Two entity types involved (most common).
• Ternary: Three entity types involved.
• Quaternary: Four or more entities involved.

Unary, Binary, Ternary Relatioonship

Entity Relationship Diagram

An Entity-Relationship Diagram (ERD) is a graphical representation of entities and their relationships. It helps visualize:

• Unary relationships: Where one entity is related to itself (e.g., Staff supervises Staff).
• Binary relationships: Common between two entities (e.g., Branch has Staff).
• Ternary relationships: Involving three entities, e.g., Supplier supplies Product to Customer.

Relationship with Attributes

Relationships can also have attributes. For example, the relationship between a Customer and Order might include an attribute such as OrderDate.