50 DBMS MCQs with Answers

Question 31

Database table by name Loan_Records is given below.

Borrower    Bank_Manager   Loan_Amount
 Ramesh      Sunderajan     10000.00
 Suresh      Ramgopal       5000.00
 Mahesh      Sunderajan     7000.00

What is the output of the following SQL query?

SELECT Count(*) 
FROM  ( ( SELECT Borrower, Bank_Manager 
          FROM Loan_Records) AS S 
          NATURAL JOIN ( SELECT Bank_Manager, Loan_Amount 
                         FROM Loan_Records) AS T );

• 3
• 9
• 5
• 6

Question 32

Database applications were built directly on top of file system to overcome the following drawbacks of using file-systems: (i) Data redundancy and inconsistency (ii) Difficulty in accessing Data (iii) Data isolation (iv) Integrity problems

• (i)
• (i) and (iv)
• (i), (ii) and (iii)
• (i), (ii), (iii) and (iv)

Question 33

Which RAID level gives block level striping with double distributed parity?

• RAID 10
• RAID 2
• RAID 6
• RAID 5

Question 34

The statement that is executed automatically by the system as a side effect of the modification of the database is

• backup
• assertion
• recovery
• trigger

Question 35

Which of the following is correct?

• B-trees are for storing data on disk and B+ trees are for main memory.
• Range queries are faster on B+ trees.
• B-trees are for primary indexes and B+ trees are for secondary indexes.
• The height of a B+ tree is independent of the number of records.

Question 36

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 ?

• 8, 8
• 120, 8
• 960, 8
• 960, 120

Question 37

Which of the following related to snowflake schema is true?

• Each dimension is represented by a single dimensional table
• Maintenance efforts are less
• Dimension tables are normalised
• It is not an extension of star schema

Question 38

Consider the following relational schema: 

Suppliers(sid:integer, sname:string, city:string, street:string)
Parts(pid:integer, pname:string, color:string)
Catalog(sid:integer, pid:integer, cost:real)

Consider the following relational query on the above database: 

SELECT S.sname
    FROM Suppliers S
        WHERE S.sid NOT IN (SELECT C.sid
                            FROM Catalog C
                            WHERE C.pid NOT IN (SELECT P.pid  
                                                FROM Parts P
                                                WHERE P.color<> \'blue\'))

Assume that relations corresponding to the above schema are not empty. Which one of the following is the correct interpretation of the above query?

• Find the names of all suppliers who have supplied a non-blue part.
  

• Find the names of all suppliers who have not supplied a non-blue part.
  

• Find the names of all suppliers who have supplied only blue parts.
  

• Find the names of all suppliers who have not supplied only blue parts.
  

• None
  

Question 39

In the index allocation scheme of blocks to a file, the maximum possible size of the file depends on :

• the size of the blocks, and the size of the ad­dress of the blocks.

• the number of blocks used for the index, and the size of the blocks.

• the size of the blocks, the number of blocks used for the index, and the size of the address of the blocks.

• None of these

Question 40

Table A
Id   Name    Age
----------------
12   Arun    60
15   Shreya  24
99   Rohit   11


Table B
Id   Name   Age
----------------
15   Shreya  24
25   Hari    40
98   Rohit   20
99   Rohit   11


Table C
Id   Phone  Area
-----------------
10   2200   02  
99   2100   01

Consider the above tables A, B and C. How many tuples does the result of the following SQL query contains?

SELECT A.id 
FROM   A 
WHERE  A.age > ALL (SELECT B.age 
                    FROM   B 
                    WHERE  B. name = "arun") 

• 4
• 3
• 0
• 1