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1.
Consider the following relation schema pertaining to a students database:
Student (rollno, name, address)
Enroll (rollno, courseno, coursename)
where the primary keys are shown underlined. The number of tuples in the Student and Enroll tables are 120 and 8 respectively. What are the maximum and minimum number of tuples that can be present in (Student * Enroll), where '*' denotes natural join ?
Enroll (rollno, courseno, coursename)
where the primary keys are shown underlined. The number of tuples in the Student and Enroll tables are 120 and 8 respectively. What are the maximum and minimum number of tuples that can be present in (Student * Enroll), where '*' denotes natural join ?
2.
The relation book (title, price) contains the titles and prices of different books. Assuming that no two books have the same price, what does the following SQL query list?
select title
from book as B
where (select count(*)
from book as T
where T.price > B.price) < 5
from book as B
where (select count(*)
from book as T
where T.price > B.price) < 5
3.
The following table has two attributes A and C where A is the primary key and C is the foreign key referencing A with on-delete cascade.
A C
-----
2 4
3 4
4 3
5 2
7 2
9 5
6 4
The set of all tuples that must be additionally deleted to preserve referential integrity when the tuple (2,4) is deleted is:
A C
-----
2 4
3 4
4 3
5 2
7 2
9 5
6 4
The set of all tuples that must be additionally deleted to preserve referential integrity when the tuple (2,4) is deleted is:
4.
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:
Query1: select student from enrolled where
student in (select student from paid)
Query2: select student from paid where
student in (select student from enrolled)
Query3: select E.student from enrolled E, paid P
where E.student = P.student
Query4: select student from paid where exists
(select * from enrolled where enrolled.student
= paid.student)
Which one of the following statements is correct?
student in (select student from paid)
Query2: select student from paid where
student in (select student from enrolled)
Query3: select E.student from enrolled E, paid P
where E.student = P.student
Query4: select student from paid where exists
(select * from enrolled where enrolled.student
= paid.student)
5.
The statement that is executed automatically by the system as a side effect of the modification of the database is
6.
Which of the following command is used to delete a table in SQL?
7.
Consider the following relational schema:
employee(empId, empName, empDept)
customer(custId, custName, salesRepId, rating)
salesRepId is a foreign key referring to empId of the employee relation. Assume that each employee makes a sale to at least one customer. What does the following query return?
SELECT empName
FROM employee E
WHERE NOT EXISTS ( SELECT custId
FROM customer C
employee(empId, empName, empDept)
customer(custId, custName, salesRepId, rating)
salesRepId is a foreign key referring to empId of the employee relation. Assume that each employee makes a sale to at least one customer. What does the following query return?
SELECT empName
FROM employee E
WHERE NOT EXISTS ( SELECT custId
FROM customer C
WHERE C.salesRepId = E.empId
AND C.rating <> `GOOD`);
AND C.rating <> `GOOD`);
8.
SQL allows tuples in relations, and correspondingly defines the multiplicity of tuples in the result of joins. Which one of the following queries always gives the same answer as the nested query shown below:
select * from R where a in (select S.a from S)
9.
Given the following statements:
S1: A foreign key declaration can always
be replaced by an equivalent check
assertion in SQL.
S2: Given the table R(a,b,c) where a and
b together form the primary key, the
following is a valid table definition.
CREATE TABLE S (
a INTEGER,
d INTEGER,
e INTEGER,
PRIMARY KEY (d),
FOREIGN KEY (a) references R)
Which one of the following statements is CORRECT?
be replaced by an equivalent check
assertion in SQL.
S2: Given the table R(a,b,c) where a and
b together form the primary key, the
following is a valid table definition.
CREATE TABLE S (
a INTEGER,
d INTEGER,
e INTEGER,
PRIMARY KEY (d),
FOREIGN KEY (a) references R)
Which one of the following statements is CORRECT?
10.
Consider a database table T containing two columns X and Y each of type integer. After the creation of the table, one record (X=1, Y=1) is inserted in the table. Let MX and My denote the respective maximum values of X and Y among all records in the table at any point in time. Using MX and MY, new records are inserted in the table 128 times with X and Y values being MX+1, 2*MY+1 respectively. It may be noted that each time after the insertion, values of MX and MY change. What will be the output of the following SQL query after the steps mentioned above are carried out?
SELECT Y FROM T WHERE X=7;
SELECT Y FROM T WHERE X=7;