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+21 votes

Consider the following functional dependencies in a database.

Date_of_Birth $\to$ Age

Age $\to$ Eligibility
Name $\to$ Roll_number Roll_number $\to$ Name
Course_number $\to$ Course_name Course_number $\to$ Instructor
(Roll_number, Course_number) $\to$ Grade  

The relation (Roll_number, Name, Date_of_birth, Age) is

  1. in second normal form but not in third normal form
  2. in third normal form but not in BCNF
  3. in BCNF
  4. in none of the above
asked in Databases by Veteran (59.9k points) | 3k views

2 Answers

+41 votes
Best answer
There are three FDs that are valid from the above set of FDs for the given relation :

Date_of_Birth $\to$ Age

Name $\to$ Roll_number

Roll_number $\to$ Name

Candidate keys for the above are : (Date_of_Birth,Name) and (Date_of_Birth, Roll_number)

Clearly there is partial dependency here (Date_of_Birth $\to$ Age) and Age is not a prime attribute. So, it is only in 1NF.

Option (D).
answered by Active (4k points)
selected by
There are also given two other fds  i.e course no ,course name and instructor.for the ck all fds should be derived from it
@Neha Singh we need to find dependency btw given relation only which is The relation (Roll_number, Name, Date_of_birth, Age) so all extra dependency other than relation no use

Prateek kumar but there may be other fd that can be indirectly derived from the attribute not present in the table thus it is always advisable to find all the possible fd's by using the closure method and see which are applicable to the given relation .

Why bcnf is not
@Jony Bhatt  When it is not in 2NF then how it can be in bcnf
+1 vote
there is partial dependency hence it is 1st normal form
answered by Junior (633 points)

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