UPPCL AE 2018:63

Question

We have a database table with relational schema $\text{R(XYZPQ)}:$

$$\begin{array}{|c|c|c|c|c|} \hline \text{X} & \text{Y} & \text{Z} & \text{P} & \text{Q} \\\hline \text{A1} & \text{B1} & \text{C1} & \text{D1} & \text{E1}  \\\hline \text{A2} & \text{B2} & \text{C1} & \text{D2} & \text{E1} \\\hline \text{A3} & \text{B2} & \text{C2} & \text{D1} & \text{E2}   \\\hline \text{A4} & \text{B3} & \text{C1} & \text{D3} & \text{E3} \\\hline \text{A5} & \text{B2} & \text{C2} & \text{D4} & \text{E2} \\\hline \end{array}$$

which of the following statement is true?

• A. $\text{ZP} \rightarrow \text{Q}$ is a functional dependency.
• B. $\text{Y} \rightarrow \text{X}$ is a functional dependency.
• C.  None of the above
• D. $\text{YZ} \rightarrow \text{P}$ is a functional dependency.

Answer 1

ZP-->Q :     ZP is unique hence hence Obviously ZP-->Q is a Functional Dependency for the instance.

 

Y-->X  :        There are 2 B2 in Y but both does not correspond to same 'X' [2nd and 3rd row] So Fail for Functional Dependency.

 

YZ-->P :      There are B2,C2(Y,Z) two times but these combination does not correspond to same 'P'.[3rd and 5th row]

 

So,A is the correct answer.