Question at position 50 An entity that connects the instances of one or more entity types and contains attributes peculiar to the relationships is called a(n): build entity.smush entity.associative entity. gateway entity.单项选择题
A
build entity.
B
smush entity.
C
associative entity.
D
gateway entity.

Question

Question at position 50 An entity that connects the instances of one or more entity types and contains attributes peculiar to the relationships is called a(n): build entity.smush entity.associative entity. gateway entity.单项选择题

A

build entity.

B

smush entity.

C

associative entity.

D

gateway entity.

BlackTom AI · Accepted Answer

An associative entity (also called a junction, bridge, or intersection entity) connects instances of two or more entity types and carries attributes that describe the relationship itself.

Relevant concepts:
- Entity types represent sets of real-world objects (e.g., Student, Course).
- Relationships link instances of entity types (e.g., a student enrolls in a course).
- When a relationship needs its own attributes (e.g., grade, enrollment_date) or when resolving a many-to-many relationship for a relational schema, an associative entity is used.

Step-by-step reasoning:
1. Identify the need: If two entities participate in a relationship that is many-to-many, or if the relationship has attributes that cannot logically belong to either participating entity, the correct modeling construct is required.
2. Decide the construct: An associative entity is introduced to represent the relationship as an entity so those relationship attributes can be stored.
3. Example mapping: Student(student_id, name), Course(course_id, title). The enrollment relationship has attributes grade and enrollment_date. Create Enrollment(student_id, course_id, grade, enrollment_date) where (student_id, course_id) forms the primary key (or a surrogate key), and student_id and course_id are foreign keys to Student and Course respectively.
4. Result: The associative entity both connects instances of the two entity types and stores the relationship-specific attributes.

Why the correct answer is correct:
- The prompt specifically asks for an entity that connects instances of one or more entity types and contains attributes peculiar to the relationships. That is precisely the definition of an associative entity.

Why the other options are incorrect:
- "build entity" and "smush entity" are not standard ER-model terms and do not describe the pattern of storing relationship attributes.
- "gateway entity" is also not a recognized term in classic ER modeling for representing relationships with attributes.

Conclusion: The correct choice is associative entity. This matches the provided answer: associative entity.

Question at position 50 An entity that connects the instances of one or more entity types and contains attributes peculiar to the relationships is called a(n): build entity.smush entity.associative entity. gateway entity.单项选择题

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