UGC NET CSE | December 2015 | Part 3 | Question: 63

Question

Consider the following three tables $R, S$ and $T.$ In this question, all the join operations are natural joins $(\bowtie )$. $(\pi )$ is the projection operation of a relation:

$\begin{array}{|ccc|} \hline & R & \\ \hline   A && B \\ \hline 1 && 2 \\ 3 && 2 \\ 5 && 6 \\ 7 & &8 \\ 9 && 8 \\ \hline \end{array} \begin{array}{|ccc|} \hline & S & \\ \hline   B && C \\ \hline 6 && 2 \\ 2 && 4 \\ 8 && 1 \\ 8 & &3 \\ 2 && 5 \\ \hline \end{array} \begin{array}{|ccc|} \hline & T & \\   \hline A && C \\ \hline 7 && 1 \\ 1 && 2 \\ 9 && 3 \\ 5 & &4 \\ 3 && 5 \\ \hline \end{array}$

Possible answer tables for this question are also given as below:

$\underset{\text{(a)}}{\begin{array}{|ccc|} \hline A & B & C \\ \hline 1 & 2& 4 \\ 1 &2& 5 \\ 3 &2& 4 \\ 3 &2& 5 \\ 5 & 6 &2 \\ 7 & 8 & 1 \\ 7 & 8 & 3 \\  9 & 8 & 1 \\ 9 & 8 & 3 \\ \hline \end{array}} \underset{\text{(b)}}{\begin{array}{|ccc|} \hline A & B & C \\ \hline 1 & 2& 2 \\ 3 &2& 5 \\ 5 &6& 4 \\ 7 &8& 1 \\ 9 & 8 &3 \\ \hline \end{array}} \underset{\text{(c)}}{\begin{array}{|ccc|} \hline A & B & C \\ \hline 1 & 6& 2 \\ 3 &2& 5 \\ 5 &2& 4 \\ 7 &8& 1 \\ 9 & 8 &3 \\ \hline \end{array}} \underset{\text{(d)}}{\begin{array}{|ccc|} \hline A & B & C \\ \hline 3 & 2& 5 \\  7 &8& 1 \\ 9 & 8 &3 \\ \hline \end{array}}$

• A. (a)
• B. (b)
• C. (c)
• D. (d)

Answer 1

A) option is option return all possible results after natural join but it does not involve the table t during natural join so false

In b )option record  5 6 4 and record 1 2 2 not possible in result so false

In c) option record 5 2 4 abd record 1 6 2 nit possible after natural join of table .

In d) option it contain partial result after joining all three table

So d option should be answer

Comments

What is the resulting table of π_A,B(R⨝T) ⨝ π_B,C(S⨝T) ?

this line is missing from question

Answer 2

Option A is the correct one..