Daily Practice Quiz-11:DBMS for GATE & PSU CS Exams

Question 1

Which of the following is used to add new attribute (column) in the existing relation schema?

Question 2

Consider the following relation R

Then identify the incorrect statement about relation R
I. The relation R has two overlapping candidate keys
II. The relation R is in 3NF
III. The relation R is in BCNF
IV. The relation R has a disadvantage of repetition of data

Question 3

When number of entities are bought together into one entity based on their similar characteristics, what is this process called

Question 4

In ER-model , weak entity meets which of the following conditions is true?

Question 5

The following table refers to search times for a key in B-trees and B⁺-trees.

A successful search means that the key exists in the database and unsuccessful means that it is not present in the database. Each of the entriesX₁, X₂, X₃ and X₄ can have a value of either Constant or Variable. Constant means that the search time is the same, independent of the specific key value, where Variable means that it is dependent on the specific key value chosen for the search.
Give the correct values for the entries X₁, X₂, X₃ and X₄ (for example X₁ =Constant, X₂= Constant, X₃ = Constant, X₄= Constant).

Question 6

A clustering index is defined on the fields which are of type

Question 7

Consider the following relations:
Student (snum: integer, sname: string, major: string, level: string, age: integer)
Class (name: string, meets at: string, room: string, ﬁd: integer)
Enrolled (snum: integer, cname: string)
Faculty (ﬁd: integer, fname: string, deptid: integer)
The meaning of these relations is straightforward; for example, Enrolled has one record per student-class pair such that the student is enrolled in the class.

Consider the following SQL statement:
S1: SELECT C.name
FROM Class C
WHERE C.room = ‘R128’
OR C.name IN
(SELECT E.cname , E.Snum
FROM Enrolled E
GROUP BY E.cname
HAVING COUNT (*) >= 5)

S2: SELECT C.name
FROM Class C
WHERE C.room = ‘R128’
OR C.name IN
(SELECT E.cname ,
FROM Enrolled E
GROUP BY E.cname
HAVING COUNT (*) >= 5)

Which of the following will result into set of student who are enrolled in course conducted in class R128 OR having five or more students enrolled in it?

Question 8

Consider the set of relations shown below and the SQL query that follows.
Students: (Roll_number, Name, Date_of_birth)
Courses: (Course number, Course_name, Instructor)
Grades: (Roll_number, Course_number, Grade)
select distinct Name
from Students, Courses, Grades
where Students. Roll_number = Grades.Roll_number
and Courses.Instructor = Korth
and Courses.Course_number = Grades.Course_number
and Grades.grade = A

Which of the following sets is computed by the above query?

Question 9

Which of the following is true regarding the following schedule S with 4 transactions?
S: r1(a); r2(b); w2(a); w2(b); w3(a); r3(c); w3(b); r1(c); w4(b); w3(c); r4(a); r4(c); w4(c); commit1; commit2;
commit3; commit4;

Question 10

Consider the following transactions with data items P and Q initialized to zero:
T₁: read (P);
read (Q);
if P = 0 then Q := Q + 1 ;
write (Q).
T₂: read (Q);
read (P);
if Q = 0 then P := P + 1 ;
write (P).
Any non-serial interleaving of T₁ and T₂ for concurrent execution leads to