The professor argues that most relationship TYPES (i.e. regarding cardinality) tend to regress to:

Question

BlackTom AI · Accepted Answer

Binary relationships involve exactly two entity types and are the simplest, most common form of relationship modeling in ER design and relational databases.

1. Relevant knowledge points and concepts
- Cardinality: describes how many instances of one entity relate to instances of another (one-to-one, one-to-many, many-to-many).
- N-ary (ternary, etc.) relationships: involve three or more entities.
- Associative (junction) entity: a table/entity used to implement many-to-many relationships by breaking them into two binary relationships.
- Relational implementation: relational tables and foreign keys naturally express links between two tables (binary links).

2. Step-by-step reasoning process
- Relational databases implement relationships by foreign keys in tables. A table with a foreign key points to one other table — that is a binary link.
- A many-to-many between A and B is implemented by creating an associative table R(A_id, B_id). Now R-A and R-B are two binary relationships.
- A ternary relationship R(A_id, B_id, C_id) is implemented as a relation with three foreign keys. Conceptually the relation R participates in three binary relationships (R–A, R–B, R–C), so the multi-way link is represented via binaries connected to R.
- In general, n-ary relationships get reified into an entity (or table) that links to each participant via binary foreign-key relationships.

3. Intermediate steps (example calculations)
- Example many-to-many: original M:N between Student and Course → create Enrollment(student_id, course_id). Result: Enrollment–Student (binary), Enrollment–Course (binary).
- Example ternary: Supply(supplier_id, part_id, project_id) stored as Supply table with three foreign keys. Each foreign key represents a binary link from Supply to the respective entity.

4. Why the correct answer is correct
Because database practice and ER decomposition routinely transform higher-arity relationships into tables/entities that connect pairwise via foreign keys, most relationship types “regress” into binary relationships in modeling and implementation.

5. Why other options are incorrect
- many-to-many, ternary, one-to-many, one-to-one, unary: these are specific relationship types, not the universal endpoint of decomposition.
- associative: is an implementation pattern (an entity) used to produce binary links, not the general regression target itself.
- weak-strong: not a standard cardinality target in this context.

6. Conclusion
The correct answer is binary, which matches the provided answer.

The professor argues that most relationship TYPES (i.e. regarding cardinality) tend to regress to:单项选择题

类似问题

Which of the following best illustrates the relationship between entities and attributes?

Question at position 46 The number of entity types that participate in a relationship is called the: degree.identifying characteristic.number.counter.

Question at position 23 The most common types of entities are:strong entities.associative entities.super entities.weak entities.

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