Exam-style question
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A relation Enrolment(StudentID, StudentName, CourseID, CourseName, Grade) has a composite primary key of StudentID and CourseID. Which decomposition best supports third normal form?.
- A.Student(StudentID, StudentName), Course(CourseID, CourseName), Enrolment(StudentID, CourseID, Grade)
- B.Student(StudentID, StudentName, CourseID), Course(CourseID, CourseName, Grade)
- C.Enrolment(StudentID, StudentName, CourseID, CourseName, Grade) with no changes
- D.Student(StudentName), Course(CourseName), Enrolment(StudentID, CourseID, Grade)
Model answer
What a good answer should say
- Student(StudentID, StudentName), Course(CourseID, CourseName), Enrolment(StudentID, CourseID, Grade)
Explanation
Why this works
StudentName depends on StudentID, CourseName depends on CourseID, and Grade depends on the whole composite key. Separating these dependencies removes partial dependencies and supports 3NF.
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