The GATE Grind

GATE 2016 CS – Question 33

Databases · Integrity Constraints and Normal Forms · 1 mark · Multiple choice

A database of research articles in a journal uses the following schema.

(Volume, Number, StartPage, EndPage, Title, Year, Price)

The primary key is (Volume, Number, StartPage, EndPage) and the following functional dependencies exist in the schema.

(Volume, Number, StartPage, EndPage) → Title

(Volume, Number) → Year

(Volume, Number, StartPage, EndPage) → Price

The database is redesigned to use the following schemas.

(Volume, Number, StartPage, EndPage, Title, Price)

(Volume, Number, Year)

Which is the weakest normal form that the new database satisfies, but the old one does not?

  1. 1NF
  2. 2NF
  3. 3NF
  4. BCNF

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Correct answer: (B) 2NF

Explanation

In the old schema, Year depends only on part of the key, (Volume, Number), which is a partial dependency, so it violates 2NF though it satisfies 1NF. The new schemas remove that partial dependency, so they satisfy 2NF. The weakest normal form satisfied by the new design but not the old one is 2NF.