What is defined as a recursive relationship in database terms?

A recursive relationship in database terms refers to a connection of a class type to itself. This type of relationship occurs when an entity in a database is related to itself in some way, allowing for scenarios where instances of a class can have associations with other instances of the same class. For example, in a human resources database, an employee might manage other employees, where both the manager and the subordinates are instances of the employee class. This self-referential aspect allows for complex data modeling and representation of relationships within the same entity.

In contrast, a connection between different class types signifies a different type of relationship and would not encapsulate the idea of recursion. Similarly, a hierarchical relationship among different entities does not imply that the entities are of the same type or class. Lastly, a relationship defined by multiple keys refers to how entities may be uniquely identified and connected through various attributes but does not address the recursive aspect inherent in this concept. Thus, the definition that accurately captures recursive relationships is one where an entity connects with itself.