Advanced Database Management System - Tutorials and Notes: Find the normal form of the given relation

Tuesday, 4 October 2016

Find the normal form of the given relation

Find the normal form of the given relation schema / Is the relation in 1NF? / Is the table in 2NF? / Is the table in 3NF? / Is the table in BCNF?


Question:


3. Assume a relation R with the schema R(A, B, C, D, E). The primary key of R is A. Which of the following is correct for R?

(a) R is in 1NF only
(b) R is in both 1NF and 2NF
(c) R is in 3NF
(d) R is in BCNF



Answer:

(b) R is in both 1NF and 2NF


As per the question,

  • Given - Schema of relation R and the key of R.
  • Not known - The set of functional dependencies
1NF - We don't need functional dependencies. Hence, we would say that R is in 1NF.
2NF - We need functional dependencies and the key for R. If the key is composite (combination of two or more attributes), we need the set of functional dependencies to determine the normal form. If the key is single attribute we don't need functional dependencies. In our question the key is A, hence we would say that R is in 2NF.

Hence, R is in both 1NF and 2NF.



R is not in 3NF (we need functional dependencies to find Transitive dependencies), and not in BCNF (we need all the Candidate keys).






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