Database-Management-System
August 29, 2024Database-Management-System
August 29, 2024Database-Management-System
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Question 844
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A many-to-one relationship exists between entity sets r1 and r2. How will it be represented using functional dependencies if Pk(r) denotes the primary key attribute of relation r?
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Pk(r1) → Pk(r2)
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Pk(r2) → Pk(r1)
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Pk(r2) → Pk(r1) and Pk(r1) → Pk(r2)
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Pk(r2) → Pk(r1) or Pk(r1) → Pk(r2)
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Question 844 Explanation:
Here, we have a many to one relationship between between Set(r1) and Set(r2).
→ Elements of Set(r2) can’t identify elements of Set(r1) because one value element in Set(r2) is pointing to more than one element of Set(r1).
→ So, we can’t say Pk(r2) → Pk(r1) but elements of Set(r1) are pointing to exactly one element of Set(r2) so we can say that Pk(r2) → Pk(r1) because r1 is uniquely identifying r2.
Correct Answer: A
Question 844 Explanation:
Here, we have a many to one relationship between between Set(r1) and Set(r2).
→ Elements of Set(r2) can’t identify elements of Set(r1) because one value element in Set(r2) is pointing to more than one element of Set(r1).
→ So, we can’t say Pk(r2) → Pk(r1) but elements of Set(r1) are pointing to exactly one element of Set(r2) so we can say that Pk(r2) → Pk(r1) because r1 is uniquely identifying r2.
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