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GATE 2014 CS (CS1) – Question 40

Databases · Integrity Constraints and Normal Forms · 2 marks · Multiple choice

S1: Every table with two single-valued attributes is in 1NF, 2NF, 3NF and BCNF. S2: AB → C, D → E, E → C is a minimal cover of AB → C, D → E, AB → E, E → C. Which is correct?

  1. S1 TRUE, S2 FALSE
  2. Both TRUE
  3. S1 FALSE, S2 TRUE
  4. Both FALSE

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Show answer and explanation

Correct answer: (A) S1 TRUE, S2 FALSE

Explanation

A two-attribute relation with atomic values is in BCNF under the conventional nonempty-determinant FD assumptions: any nontrivial FD makes its determinant a key. S2 removes AB→E even though it cannot be derived from AB→C,D→E,E→C. Therefore **S1 true,S2 false,A**. Allowing empty determinants requires qualification of the first statement.