1
GATE CSE 1999
MCQ (Single Correct Answer)
+2
-0.6
Which of the following is/are correct?
A
An SQL query automatically eliminates duplicates.
B
An SQL query will not work if there are no indexes on the relations.
C
SQL permits attribute names to be repeated in the same relation.
D
None of the above.
2
GATE CSE 1999
Subjective
+2
-0
Consider the set of relations

EMP (Employee-no, Dept-no, Employee-name, Salary)
DEPT (Dept-no, Dept-name, Location)

Write an SQL query to:

(a) Find all employee names who work in departments located at "Calcutta" and whose salary is greater than Rs.50,000.

(b) Calculate, for each department number, the number of employees with a salary greater than Rs.1,00,000.

3
GATE CSE 1999
MCQ (Single Correct Answer)
+1
-0.3
Consider the join of a relation R with a relation S. If R has m tuples and S has n tuples then the maximum and minimum sizes of the join respectively are
A
m + n and 0
B
mn and 0
C
m + n and |m – n|
D
mn and m + n
4
GATE CSE 1999
MCQ (Single Correct Answer)
+1
-0.3

The relational algebra expression equivalent to the following tuple calculus expression:

$$\left\{ {t|t \in r \wedge \left( {t\left[ A \right] = 10 \wedge t\left[ B \right] = 20} \right)} \right\}$$ is:
A
$${\sigma _{\left( {A = 10 \vee B = 20} \right)}}\left( r \right)$$
B
$${\sigma _{\left( {A = 10} \right)}}\left( r \right) \cup {\sigma _{\left( {B = 20} \right)}}\left( r \right)$$
C
$${\sigma _{\left( {A = 10} \right)}}\left( r \right) \cap {\sigma _{\left( {B = 20} \right)}}\left( r \right)$$
D
$${\sigma _{\left( {A = 10} \right)}}\left( r \right) - {\sigma _{\left( {B = 20} \right)}}\left( r \right)$$
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