Describe the relationship between COURSE and DEPARTMENT

Question

BlackTom AI · Accepted Answer

The COURSE table contains deptnumber as a foreign key referencing DEPARTMENT.deptnumber, so each course is tied to a single department.

1. Relevant knowledge points and concepts
- Primary key (DEPARTMENT.deptnumber) uniquely identifies a department.
- Foreign key (COURSE.deptnumber) creates a referential link from a course to a department.
- Cardinality/participation notation (straight line vs. circle; crow’s foot) indicates whether the relationship is mandatory/optional and one-or-many.

2. Step-by-step reasoning
- Inspect the COURSE attributes: cnumber (PK) and deptnumber (FK).
- The deptnumber in COURSE points to DEPARTMENT.deptnumber, so each COURSE row references one DEPARTMENT row.
- The ER notation shows a single straight line (not an optional circle) on the COURSE→DEPARTMENT connection, indicating the relationship is mandatory on the course side (no null allowed).
- The department side shows a crow’s foot toward COURSE, indicating one department can be related to many courses.

3. Intermediate “calculation” / inference steps
- Because COURSE contains exactly one deptnumber field (not a set), structurally a course cannot reference more than one department.
- Because deptnumber is mandatory (non-null), a course must reference a department rather than zero.
- Therefore the multiplicity from COURSE to DEPARTMENT is exactly one (1..1).

4. Why the correct answer is correct
- The presence of a non-null foreign key deptnumber in COURSE guarantees each course is offered by one and only one department. The ER notation confirms this by showing mandatory one on the course side and many on the department side.

5. Why other options are incorrect (brief)
- “0 to 1 Department” would allow course.deptnumber to be null — not shown here.
- “1 to Many Departments” or “Many Departments” would require multiple dept references per course — not present.
- “0 to Many” or “Many Courses are offered by Many Departments” contradicts the single deptnumber FK.
- “No relationship” contradicts the explicit FK and ER link.

6. Conclusion / confirmation
- The correct relationship is: 1 Course is offered by 1 and only 1 Department (matches the provided answer).

Describe the relationship between COURSE and DEPARTMENT单项选择题

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