Which statement below is likely to be true?

Question

BlackTom AI · Accepted Answer

Let’s examine each statement in turn to determine which is likely true about relationships in an ER model.
Option a: 'Employee manages Employee is an example of Binary relationship' A binary relationship involves two distinct entities or two instances of entities. While 'Employee manages Employee' might seem to involve two employees, it is typically interpreted as a recursive (or unary) relationship because the same entity type (Employee) participates more than once in the relationship (one employee managing another). Calling it binary would be inaccurate since both sides reference the same entity type; the more precise classification is recursive/unary, not binary.
Option b: 'Binary relationship also known as recursive relationship' This is a common point of confusion. A binary relationship involves two different entities (or two roles of possibly the same entity type but connected to two distinct entity instances). A recursive relationship is a special case where an entity participates in the relationship with itself, often described as unary or recursive, not strictly binary. Therefore, this statement is not correct as a general definition of binary relationships.
Option c: 'Binary relationship exists when three entities are associated' This statement misstates the core idea: a binary relationship connects two entities (it could be instances of two (potentially the same) entity types). A relationship involving three entities would be trinary (or ternary), not binary. So this option is false.
Option d: 'Unary relationship involves only one entity' This statement correctly identifies unary (also called recursive) relationships, where a single entity type participates in the relationship with itself, often in a one-to-many or many-to-many fashion depending on the scenario. Hence this option accurately describes a unary relationship.

In summary, the false choices mischaracterize the nature of relationship types by conflating binary with recursive, misdefining binary scope, or describing a trinary case as binary, while the true concept is that a unary relationship involves only one entity participating in the relationship.

Introduction to Databases (032025-LCP)

Which statement below is likely to be true?

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