Aunary relationship(also known as arecursive relationship) occurs when an entityrelates to itself.

Example Usage:

Employees and Managers:

sql

CREATE TABLE Employees (

EmpID INT PRIMARY KEY,

Name VARCHAR(50),

ManagerID INT,

FOREIGN KEY (ManagerID) REFERENCES Employees(EmpID)

);

Here, ManagerIDreferences another Employee→ aunary (self-referential) relationship.

Why Other Options Are Incorrect:

Option A (Modality) (Incorrect):Describesoptional vs. mandatoryrelationships, not self-referencing.

Option C (Cardinality) (Incorrect):Defines how many instances relate,not the type of relationship.

Option D (Binary) (Incorrect):Binary relationships involvetwo different entities, not self-referencing.

Thus, the correct answer isUnary, as it describesrelationships within the same entity type.