The GATE Grind

GATE 2014 CS (CS3) – Question 32

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

A prime attribute of relation schema R appears ______.

  1. in all candidate keys of R
  2. in some candidate key of R
  3. in a foreign key of R
  4. only in the primary key of R

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Correct answer: (B) in some candidate key of R

Explanation

An attribute is prime when it belongs to at least one candidate key. Therefore **B**, some candidate key, is the definition. It need not belong to every candidate key or to the particular key selected as primary.