What is a defining feature of a unary relationship?

What is a defining feature of a unary relationship?

• A. Involves two different entities
• B. Represents relationships among multiple entities
• C. Involves only one entity and may include hierarchy
• D. Is exclusively a many-to-many relationship

Answer: (C)

A unary relationship is characterized by involving only a single entity in relation to itself. This type of relationship illustrates how instances of the same entity can interact. For example, in a corporate structure, an employee might supervise other employees, all of whom belong to the same entity "Employee." This demonstrates how an employee can have relationships with other employees, thus forming a hierarchy or even recursive relationships within that same entity. The other options do not capture the essence of what a unary relationship entails. A unary relationship cannot involve two different entities, as that would suggest a binary relationship. Similarly, while unary relationships can certainly represent various hierarchies, they don't represent relationships among multiple distinct entities; they focus solely on one entity and its internal relations. Lastly, claiming a unary relationship is exclusively a many-to-many relationship is also inaccurate, as unary relationships can also be one-to-one or one-to-many, depending on the context of how the instances relate to each other within the same entity framework.

A unary relationship is characterized by involving only a single entity in relation to itself. This type of relationship illustrates how instances of the same entity can interact. For example, in a corporate structure, an employee might supervise other employees, all of whom belong to the same entity "Employee." This demonstrates how an employee can have relationships with other employees, thus forming a hierarchy or even recursive relationships within that same entity.

The other options do not capture the essence of what a unary relationship entails. A unary relationship cannot involve two different entities, as that would suggest a binary relationship. Similarly, while unary relationships can certainly represent various hierarchies, they don't represent relationships among multiple distinct entities; they focus solely on one entity and its internal relations. Lastly, claiming a unary relationship is exclusively a many-to-many relationship is also inaccurate, as unary relationships can also be one-to-one or one-to-many, depending on the context of how the instances relate to each other within the same entity framework.