Official PYQ · 2014Set 2 · Q22Integrity ConstraintsNAT1 mark

GATE CS 2014 Set 2 Q22 — Integrity Constraints

Given an instance of the STUDENTS relation as shown as below

\begin{array}{|c|c|c|c|c|} \hline \textbf{StudentID} & \textbf{StudentName} & \textbf{StudentEmail} & \textbf{StudentAge} & \textbf{CPI} \\ \hline \text{2345} & \text{Shankar} & \text{shankar@math} & \text{X} & \text{9.4}\\ \hline\text{1287} & \text{Swati} & \text{swati@ee} & \text{19} & \text{9.5}\\ \hline\text{7853} & \text{Shankar} & \text{shankar@cse} & \text{19} & \text{9.4} \\ \hline \text{9876} & \text{Swati} & \text{swati@mech} & \text{18} & \text{9.3} \\ \hline \text{8765} & \text{Ganesh} & \text{ganesh@civil} & \text{19} & \text{8.7} \\ \hline \end{array}

For

(\text{StudentName, StudentAge})

to be a key for this instance, the value

X

should NOT be equal to______.

View worked solution

Answer: 19

For a set of attributes to be a key for a relation instance, the values of those attributes must be unique for every tuple in that instance.

Let us list the values of the attribute pair $(\text{StudentName}, \text{StudentAge})$ for each of the five tuples in the given relation:

For $(\text{StudentName}, \text{StudentAge})$ to be a key, all five pairs must be distinct:

Comparing tuple 1 and tuple 3: if $X = 19$ , both tuples will have the same pair $(\text{Shankar}, 19)$ . This violates the uniqueness property of a key.
For any value of $X \neq 19$ , the pair $(\text{Shankar}, X)$ remains unique in the relation.

Thus, the value of $X$ should NOT be equal to 19.

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Published 10 Oct 2026

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