1
GATE CSE 2008
MCQ (Single Correct Answer)
+2
-0.6

Consider The Following Relational Scheme

Student (school-id, sch-roll-no, sname, saddress)
School (school-id, sch-name, sch-address, sch-phone)
Enrolment (school-id, sch-roll-no, erollno, examname)
ExamResult (Erollno, examname, marks)

What does the following SQL query output?
SELECT sch-name, COUNT (*) 
FROM School C, Enrolment E, 
ExamResult R 
WHERE E.school-id = C.school-id 
AND E.examname = R.examname 
AND E.erollno = R.erollno
AND R.marks = 100 AND S.school-id IN 
(SELECT school-id 
 FROM student 
 GROUP BY school-id 
 HAVING COUNT (*) > 200) 
GROUP BY school-id;
A
for each school with more than 200 students appearing in exams, the name of the school and the number of 100s scored by its students
B
for each school with more than 200 students in it, the name of the school and the number of 100s scored by its students
C
for each school with more than 200 students in it, the name of the school and the number of its students scoring 100 in at least one exam
D
nothing; the query has a syntax error
2
GATE CSE 2007
MCQ (Single Correct Answer)
+2
-0.6
Consider the table employee(empId, name, department, salary) and the two queries Q1, Q2 below. Assuming that department 5 has more than one employee, and we want to find the employees who get higher salary than anyone in the department 5, which one of the statements is TRUE for any arbitrary employee table?
Q1:
Select e.empId 
From employee e 
Where not exists 
  (Select * From employee s
   where s.department = "5" and 
   s.salary >=e.salary);
Q2:
Select e.empId 
From employee e 
Where e.salary > Any 
( Select distinct salary 
From employee s 
Where s.department = "5");
A
Q1 is the correct query.
B
Q2 is the correct query.
C
Both Q1 and Q2 produce the same answer.
D
Neither Q1 nor Q2 is the correct query.
3
GATE CSE 2006
MCQ (Single Correct Answer)
+2
-0.6
Consider the relation account (customer, balance) where customer is a primary key and there are no null values. We would like to rank customers according to decreasing balance. The customer with the largest balance gets rank 1. Ties are not broke but ranks are skipped: if exactly two customers have the largest balance they each get rank 1 and rank 2 is not assigned.
Query1:
  Select A.customer, count(B.customer)
  From account A, account B
  Where A.balance <=B.balance
  Group by A.customer

Query2:
  Select A.customer, 1+count(B.customer)
  From account A, account B
  Where A.balance < B.balance
  Group by A.customer

Consider these statements about Query1 and Query2.

1. Query1 will produce the same row set as Query2 for some but not all databases.

2. Both Query1 and Query2 are correct implementation of the specification

3. Query1 is a correct implementation of the specification but Query2 is not

4. Neither Query1 nor Query2 is a correct implementation of the specification

5. Assigning rank with a pure relational query takes less time than scanning in decreasing balance order assigning ranks using ODBC.

Which two of the above statements are correct?

A
2 and 5
B
1 and 3
C
1 and 4
D
3 and 5
4
GATE CSE 2006
MCQ (Single Correct Answer)
+2
-0.6

Consider the relation "enrolled (student, course)" in which (student, course) is the primary key, and the relation "paid (student, amount)" where student is the primary key. Assume no null values and no foreign keys or integrity constraints. Given the following four queries:

Query 1:

Select student 
from enrolled 
where student in (select student from paid)

Query 2:

Select student 
from paid 
where student in (select student from enrolled)

Query 3:

Select E.student 
from enrolled E, paid P 
where E.student = P.student

Query 4:

Select student 
from paid 
where exists (Select * 
              from enrolled 
              where enrolled.student = paid.student)

Which one of the following statements is correct?

A
All queries return identical row sets for any database
B
Query 2 and Query 4 return identical row sets for all databases but there exist databases for which Query 1 and Query 2 return different row sets.
C
There exist databases for which Query 3 returns strictly fewer rows than Query 2
D
There exist databases for which Query 4 will encounter an integrity violation at runtime.
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