edited by
7,205 views
33 votes
33 votes
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______.
edited by

3 Answers

Best answer
47 votes
47 votes
Should not eqaul to $19$.

Since if it is equal the same key will have two different values for "StudentEmail" which cannot be true by the definition of candidate/primary/super key.
edited by
8 votes
8 votes
There is already an entry with same name and age as 19. So the age of this entry must be something other than 19.
2 votes
2 votes
X Is NOt Equal 19

 

Because Primary Key  unique Key It Uniquely Identify All Tuples If It is  19  It has Same Value As Another Tuple So  Other Then 18 Id Preferble
Answer:

Related questions

34 votes
34 votes
8 answers
1
go_editor asked Sep 28, 2014
11,331 views
The maximum number of superkeys for the relation schema $R(E,F,G,H)$ with $E$ as the key is _____.
39 votes
39 votes
4 answers
2
go_editor asked Sep 28, 2014
13,023 views
A prime attribute of a relation scheme $R$ is an attribute that appearsin all candidate keys of $R$in some candidate key of $R$in a foreign key of $R$only in the primary ...
25 votes
25 votes
3 answers
3
go_editor asked Sep 28, 2014
9,754 views
The number of distinct positive integral factors of $2014$ is _____________
27 votes
27 votes
5 answers
4
go_editor asked Sep 28, 2014
11,369 views
Consider the function func shown below: int func(int num) { int count = 0; while (num) { count++; num>>= 1; } return (count); }The value returned by func($435$) is ______...