Question 1

In SQL, a relation can contain null values, and comparisons with null values are treated as unknown. If all the comparisons with null values are treated as false, which of the following pairs is equivalent?

x = 10 not (not x = 10)
x = 10, x > 9 and x < 11, where x is an integer
x $\ne$ 10 not (x = 10)
Both (1) and (2)

Answer

Correct Option: D

Question 2

If the strings of the language L can be effectively enumerated in lexicographic (i.e. alphabetic) order, which of the following statements is true?

L is necessarily finite.
L is regular but not necessarily finite.
L is context free but not necessarily regular.
L is recursive but not necessarily context free.

Answer

Correct Option: A

Question 3

Which command is the fastest among the following?

COPY TO < New File >
COPY FILE < File 1 > < File 2 >
COPY STRUCTRUE TO <new file >
COPY TO M FILE - DAT DELIMITED

Answer

Correct Option: C

Question 4

What happens when the structure of a database file, with 20 records, is modified?

? BOF ( ) Prints F
? EOF ( ) Prints F
? BOF ( ) Prints T
? EOF ( ) Prints T

Answer

Correct Option: D

Question 5

Consider the following SQL query

Select distinct $a_1, a_2, …, a_n$

from $r_1, r_2, …, r_m$

where P

For an arbitrary predicate P, this query is equivalent to which of the following relational algebra expressions?

$\Pi_{a_1, a_2, … a_n} \sigma_p \left(r_1 \times r_2 \times \dots \times r_m\right)$
$\Pi_{a_1, a_2, … a_n} \sigma_p \left(r_1 \bowtie r_2 \bowtie \dots \bowtie r_m \right)$
$\Pi_{a_1, a_2, … a_n} \sigma_p \left(r_1 \cup r_2 \cup \dots \cup r_m \right)$
$\Pi_{a_1, a_2, … a_n} \sigma_p \left(r_1 \cap r_2 \cap \dots \cap r_m \right)$

Answer

Correct Option: A

Question 6

In the Join of a relation P with a relation Q, P has 'm' tuples and Q has 'n' tuples. Then, the maximum and minimum sizes of the Join (respectively), are

m + n and 0
mn and 0
m + n and |m - n|
mn and m + n

Answer

Correct Option: B

Question 7

Define languages L₀ and L₁ as follows: L₀ = {M, w, 0 > 1 M halts on w} L₀ = {M, w, 0 > 1 M does not halts on w} Here < M, u, I > is a triplet, whose first component M is an encoding of a Turing machine, second component, w, is a string and third component, I, is a bit Let L = L_0$\cup$L₁, which of the following is true?

L is recursively enumerable, but $\bar L$is not.
$\bar L$is recursively enumerable, but L is not.
Both L and $\bar L$ are recursive.
Neither L nor $\bar L$ is recursively enumerable.

Answer

Correct Option: A

Question 8

Which of the following is a valid first order formula? (Here (\alpha) and (\beta) are first order formulae with $x$ as their only free variable)

((∀x)[α] ⇒ (∀x)[β]) ⇒ (∀x)[α ⇒ β]
(∀x)[α] ⇒ (∃x)[α ∧ β]
((∀x)[α ∨ β] ⇒ (∃x)[α]) ⇒ (∀x)[α]
(∀x)[α ⇒ β] ⇒ ((∀x)[α]) ⇒ (∀x)[β])

Answer

Correct Option: D

Question 9

Which normal form is not considered adequate for the normal relational database design?

2 NF
5 NF
3 NF
Both (1) and (2)

Answer

Correct Option: D

Question 10

Consider the following logic program P A(x) <- B(x, y), C(y) <- B(x,x) Which of the following first order sentences is equivalent to P?

(∀x)[(∃y)[B(x,y)∧C(y)]⇒A(x)]∧¬(∃X)[B(x,x)]
(∀x)[(∀y)[B(x,y)∧C(y)]⇒A(x)]∧¬(∃X)[B(x,x)]
(∀x)[(∃y)[B(x,y)∧C(y)]⇒A(x)]∨¬(∃X)[B(x,x)]
(∀x)[(∀y)[B(x,y)∧C(y)]⇒A(x)]∧(∃X)[B(x,x)]

Answer

Correct Option: C

Question 11

Let R (a, b, c) and S (d, e, f) be the two relations in which d is the foreign key of S that refers to the primary key of R. Consider the following four operations regarding R and S; A. Insert into R B. Insert into S C. Delete from R D. Delete from S Which of the following is true about the above referential integrity constraint?

None of these can cause its violation.
All of these can cause its violation.
Both (1) and (4) can cause its violation.
Both (2) and (3) can cause its violation.

Answer

Correct Option: D

Question 12

How much bandwidth is there in 0.2 micron of spectrum at a wavelength of 1 micron?

60,000 GHz
15,000 GHz
30,000 GHz
40,000 GHz

Answer

Correct Option: A

Question 13

Consider the following dependencies in a database:
Date_of_Birth$\rightarrow$Age Age$\rightarrow$Eligibility Name$\rightarrow$Roll_number Roll_number $\rightarrow$ Name Course_ number $\rightarrow$Courses_ name Course_ number$\rightarrow$Instructor (Roll_number; Courses_ name) $\rightarrow$Grade The relation (Roll_number, Name, Date_of_Birth, age) is

in second normal form but not in third normal form
in third normal form but not in BCNF
in BCNF
in none of the above

Answer

Correct Option: A

Question 14

To have a file, which holds a list, it is necessary to

identify the record in the list
identify the name, width and type of the fields of each record
identify the file in a record
both (1) and (2)

Answer

Correct Option: D

Question 15

Which of the following does not find all the customers who have a loan amount more than 1200?

{t (Customer name) / t $\in$ borrow $\land$ t [amount] > 1200}
{t / t(Customer name) $\in$ borrow $\land$ t [amount] > 1200}
{t / $\exists$ s $\in$ borrow (t[Customer name] = s[Customer name]) $\land$ s[amount] > 1200)}
Both (1) and (2)

Answer

Correct Option: D

Description: GATE Exam Online Practice Test Database Management System(DBMS)
Number of Questions: 15
Created by: Aliensbrain Bot
Tags: DBMS GATE CS

Online Test - 3 Database Management System

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