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Online Test - 4 Database Management System

GATE Online Exam Practice Test Database Management System (DBMS)

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Questions

Question 1 Multiple Choice (Single Answer)

Which of the following scenarios may lead to an irrecoverable error in a database system?

  1. A transaction writes a data item after it is read by an uncommitted transaction.
  2. A transaction reads a data item after it is read by an uncommitted transaction.
  3. A transaction reads a data item after it is written by a committed transaction.
  4. A transaction reads a data item after it is written by an uncommitted transaction.
Question 2 Multiple Choice (Single Answer)

What happens when a primary key is combined with a foreign key?

  1. It connects network model between the tables that connect them.
  2. It connects many-to-many relationship between the tables that connect them.
  3. It connects parent child relationship between the tables that connect them.
  4. None of these
Question 3 Multiple Choice (Single Answer)

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
Courses. Courses_ number = Grades
Courses_ number and Grades. grade = A

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

  1. Names of students who have got A grade in all courses taught by Korth.
  2. Names of students who have got A grade in all courses.
  3. Names of students who have got A grade in at least one of the courses taught by Korth.
  4. None of above
Question 4 Multiple Choice (Single Answer)

Which of the following does the database administrator coordinate?

  1. DBMS and data base
  2. Application program and data base
  3. Data base and users
  4. Application program and users
Question 5 Multiple Choice (Single Answer)

A relational database, which is in 3NF, may have undesirable data redundancy because there may exist

  1. non-trivial functional dependencies involving prime attributes on the right side
  2. non -trivial functional dependencies involving only prime attributes
  3. either (1) or (2)
  4. both (1) and (2)
Question 6 Multiple Choice (Single Answer)

Which of the following relationship calculus-expressions is not safe?

  1. $\left\\\{t \mid \exists u \in R_1\left(t[A] = u[A]\right) \land \neg \exists s \in R_2 \left(t[A] = s[A]\right)\right\\\}$
  2. $\left\\\{t \mid \neg (t \in R_1)\right\\\} $
  3. $\left\\\{t \mid \exists u \in R_1\left(t[A]=u[A]\right) \land \exists s \in R_2 \left(t[A] = s[A]\right)\right\\\}$
  4. Both (1) and (3) are safe.
Question 7 Multiple Choice (Single Answer)

Consider a relation geq, which represents “greater than or equal to”, i.e. (x, y)$\in$ geq only if y > = x.
Create table geq:
(
lb integer not null
ub integer not null
primary key lb
foreign key (ub) references geq on delete cascade
)

If a tuple (x, y) is deleted, which of the following is possible?

  1. A tuple (z, w), with z > y is deleted.
  2. A tuple (z, w), with z > x is deleted.
  3. A tuple (z, w), with w < x is deleted.
  4. The deletion of (x, y) is prohibited.
Question 8 Multiple Choice (Single Answer)

These are five records in a data base:

     
Name Age Occupation Category
Neha 23 CON A
Dhruti 24 ENG B
Sonika 25 DOC C
Poonam 26 SER D

There is an index file associated with this and it contains the values: 1, 3, 2, 4. Which of the following fields is the index built form?

  1. Age
  2. Name
  3. Occupation
  4. Category
Question 9 Multiple Choice (Single Answer)

Given relations: $\gamma$ (w, x) and S (y, z), the result of select distinct w, x. From r, S is guaranteed to be the same as $\gamma$, empty. Which among the following is correct?

  1. $\gamma$ has no duplicates and s is non empty.
  2. $\gamma$ and s have no duplicates.
  3. S has no duplicates and $\gamma$ is non empty.
  4. $\gamma$ and S have the same number of tuples.
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