Database-Management-System
August 26, 2024ER-Model
August 26, 2024Database-Management-System
| Question 632 |
The completeness constraint has rules :
| Supertype, Subtype | |
| Total specialization, Partial specialization | |
| Specialization, Generalization | |
| All of the above |
Question 632 Explanation:
→ Completeness constraints are both total specialization and partial specialization.
→ The completeness constraints decide whether a supertype instance must also be a membe of at least one subtype.
→ The total specialization rule demands that every entity in the superclass belong to some subclass. Just as with a regular ERD, total specialization is symbolized with a double line connection between entities.
→ The partial specialization rule allows an entity to not belong to any of the subclasses. It is represented with a single line connection.
→ The completeness constraints decide whether a supertype instance must also be a membe of at least one subtype.
→ The total specialization rule demands that every entity in the superclass belong to some subclass. Just as with a regular ERD, total specialization is symbolized with a double line connection between entities.
→ The partial specialization rule allows an entity to not belong to any of the subclasses. It is represented with a single line connection.
Correct Answer: B
Question 632 Explanation:
→ Completeness constraints are both total specialization and partial specialization.
→ The completeness constraints decide whether a supertype instance must also be a membe of at least one subtype.
→ The total specialization rule demands that every entity in the superclass belong to some subclass. Just as with a regular ERD, total specialization is symbolized with a double line connection between entities.
→ The partial specialization rule allows an entity to not belong to any of the subclasses. It is represented with a single line connection.
→ The completeness constraints decide whether a supertype instance must also be a membe of at least one subtype.
→ The total specialization rule demands that every entity in the superclass belong to some subclass. Just as with a regular ERD, total specialization is symbolized with a double line connection between entities.
→ The partial specialization rule allows an entity to not belong to any of the subclasses. It is represented with a single line connection.