GATE CSE 2022 Q14: Which normal-form statement is always true

In a relational data model, which one of the following statements is TRUE?

Try it: multiple choice: exactly one correct option

Wrong answer costs 1/3 mark in GATE.

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Answer: A (official GATE 2022 final answer key)

Concept used: BCNF requires the left side of every non-trivial FD to be a superkey; all-prime relations are only guaranteed 3NF.

First step: List the possible non-trivial FDs on $R(A, B)$ : $A \to B$ makes $A$ a key, $B \to A$ makes $B$ a key.

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Source: official GATE 2022 CS question paper and final answer key, organised by IIT Kharagpur. Question paper · Answer key