Given the relation X below

X: $\begin{array} { l l l }
\mathrm { A } & \mathrm { B } & \mathrm { C } \
\hline 2 & 5 & 7 \
3 & 3 & 3 \
4 & 4 & 2 \
5 & 2 & 8
\end{array}$
What value will be retrieved by the following query?
TEMP ? SELECT from X where B = C
RESULT ? PROJECT B from TEMP
A) 2
B) 3
C) 4
D) 5

Question

Given the relation X below

X: $\begin{array} { l l l } 
\mathrm { A } & \mathrm { B } & \mathrm { C } \
\hline 2 & 5 & 7 \
3 & 3 & 3 \
4 & 4 & 2 \
5 & 2 & 8
\end{array}$
What value will be retrieved by the following query?
TEMP ? SELECT from X where B = C
RESULT ? PROJECT B from TEMP
A) 2
B) 3
C) 4
D) 5

Quizplus · Accepted Answer

In the given relation X, B = 1, C = 2, so no tuple will satisfy the condition B = C in the SELECT operation. Therefore, an empty table will be returned. And, the PROJECT operation on an empty table will also result in an empty table. So, the final output will be an empty table.

Given the Relation X Below X ABC257333442528\begin{array} { l l l } \mathrm { A } & \mathrm { B } & \mathrm { C } \\\hline 2 & 5 & 7 \\3 & 3 & 3 \\4 & 4 & 2 \\5 & 2 & 8\end{array}A2345​B5342​C7328​​

Given the Relation X Below

X $\begin{array} { l l l } \mathrm { A } & \mathrm { B } & \mathrm { C } \\\hline 2 & 5 & 7 \\3 & 3 & 3 \\4 & 4 & 2 \\5 & 2 & 8\end{array}$