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Consider the following functional dependencies in a database.$$\begin{array}{|l|l|}\hline \text{Date_of_Birth } \to \text{Age} & \text{Age } \to \text{Eligibility} \\\hline  \text{Name } \to \text{Roll_number} & \text{Roll_number }\to \text{Name} \\\hline   \text{Course_number }\to \text{Course_name} & \text{Course_number } \to\text{Instructor} \\\hline  \text{(Roll_number, Course_number) }\to\text{Grade} & \text{}  \\\hline \end{array}$$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
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3 Answers

Best answer
77 votes
77 votes

There are three FDs that are valid from the above set of FDs for the given relation :

  1. Date_of_Birth $\to$ Age
  2. Name $\to$ Roll_number
  3. 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 in 1NF only.

Option (D).

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2 votes

Here, Date of Birth which is a part of the candidate key derives a non-prime attribute, i.e. Part of CK --> Non-Prime attribute.

Therefore PARTIAL DEPENDENCY, not in 2NF.

1 votes
1 votes
there is partial dependency hence it is 1st normal form
Answer:

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