Data Modeling With Er Model - Study Mode
[#1] Which of the following indicates the maximum number of entities that can be involved in a relationship?
Correct Answer
(B) Maximum cardinality
Explanation
Solution: Option A: Minimum cardinality Minimum cardinality defines the least number of entities that must participate in a relationship. It typically specifies the mandatory aspect of a relationship. For instance, in an employee-manager relationship, a department may need at least one manager. Option B: Maximum cardinality Maximum cardinality indicates the upper limit on the number of entities that can participate in a relationship. It specifies the maximum number of instances an entity can be associated with another entity in a relationship. For example, in a one-to-many relationship, the maximum cardinality would denote the "many" side of the relationship. Option C: ERD ERD stands for Entity-Relationship Diagram, which is a graphical representation of entities and their relationships. While ERDs visually display cardinality, they are not the direct indicators of the maximum number of entities in a relationship. Option D: Greater Entity Count (GEC) This option is not a standard term in data modeling or the ER model. It does not pertain to defining the number of entities involved in a relationship. Conclusion: The correct answer is Option B: Maximum cardinality because it directly specifies the maximum number of entities that can be involved in a relationship.
[#2] Which type of entity cannot exist in the database unless another type of entity also exists in the database, but does not require that the identifier of that other entity be included as part of its own identifier?
Correct Answer
(D) ID- independent entity
Explanation
Solution: Option A: Weak entity A weak entity is an entity that cannot exist in the database unless it is associated with a strong entity. However, it typically requires the identifier of the associated strong entity to form its own identifier, making this option incorrect for the given question. Option B: Strong entity A strong entity is an entity that can exist independently in the database without relying on any other entity. Since the question specifies dependency on another entity, this option does not fit the criteria. Option C: ID-dependent entity An ID-dependent entity requires the identifier of another entity as part of its own identifier. This does not align with the condition in the question where the dependent entity does not require the identifier of the associated entity. Option D: ID-independent entity An ID-independent entity cannot exist in the database unless another type of entity exists, but it does not require the identifier of the associated entity to be part of its own identifier. This perfectly matches the criteria described in the question. Conclusion: The correct answer is Option D: ID-independent entity because it satisfies the condition of dependency without including the identifier of the related entity in its own identifier.
[#3] In a one-to-many relationship, the entity that is on the one side of the relationship is called a(n) ________ entity.
Correct Answer
(A) parent
Explanation
Solution: Option A: Parent In a one-to-many relationship, the entity on the one side of the relationship is typically referred to as the "parent" entity. It acts as the primary entity that relates to multiple entities on the "many" side. For example, in a department-employee relationship, the department is the parent entity. Option B: Child The "child" entity is on the "many" side of the relationship in a one-to-many relationship. It depends on the parent entity and can have multiple instances associated with a single instance of the parent entity. This does not apply to the entity on the one side. Option C: Instance An "instance" refers to a single occurrence of an entity, not the classification of an entity within a relationship. Therefore, it is not relevant to identifying the role of the entity on the one side of the relationship. Option D: Subtype A "subtype" is used in an entity-relationship model to represent specialized versions of a general entity (supertype). It is unrelated to the roles in a one-to-many relationship. Conclusion: The correct answer is Option A: Parent because the entity on the one side of a one-to-many relationship is referred to as the parent entity.
[#4] Which type of entity represents an actual occurrence of an associated generalized entity?
Correct Answer
(D) Instance entity
[#5] A recursive relationship is a relationship between an entity and ________ .
Correct Answer
(A) itself