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Indicate which of the following statements are true:

A relational database which is in $3$NF may still have undesirable data redundancy because there may exist:

  1. Transitive functional dependencies
  2. Non-trivial functional dependencies involving prime attributes on the right-side.
  3. Non-trivial functional dependencies involving prime attributes only on the left-side.
  4. Non-trivial functional dependencies involving only prime attributes.
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If we talk on the basis of Redundancy hierarch , then BCNF(according to gate Syllabi) is on TOP , means if a relationis in BCNF then it is free from redundancy.

As the given Ques says that table is already in 3NF , so there should be no Partial dependency and no transitive dependency.(rule of 3 NF).

Now, for a relation to be in BCNF we must satisfy:

  • X → Y is a trivial functional dependency (Y ⊆ X)
  • X is a super key for schema R.

So the answer should be B,C,D

because Prime attributes are the attributes of the candidate key which defines the uniqueness (Eg: SSN number in a employee database) , they are not candidate key nor form a superkey.

Note: If i am wrong then some moderator or required people can correct me.

Answer:

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