Database Questions and Answers – Querying database part-2 DML

This set of Database Questions & Answers focuses on “Querying database part-1 DML”

The instructor relation

ID Name Dept_name Salary
10101 Hayley Comp.Sci. 65000
12121 Jackson Finance 90000
15151 Nathan Music 87000
22222 April Biology 73000
34345 Crick Comp.Sci. 100000

The course relation

Course_id Title Dept_name Credits
CS-101 Robotics Comp.Sci. 5
BIO-244 Genetics Biology 4
PHY-333 Physical Principles Physics 3
MUS-562 Music Video Production Music 2
FIN-101 Investment Banking Finance 3

Answer the questions based on the above relations

1. Which of the following command is used to display the departments of the instructor relation?
a) Select * from instructor where Dept_name = Finance;
b) Select * from instructor ;
c) Select dept_name from instructor;
d) Select dept_name for instructor where Name=Jackson;
View Answer

Answer: c
Explanation: Only one field is necessary for the query and where clause is not needed for the selection.

2. How can we select the elements which have common Dept_name in both the relation ?
a) Select * from instructor i , course c where i.Dept_name=c.Dept_name;
b) Select Dept name from instructor ,Course ;
c) Select * from instructor i , course c ;
d) Select Dept_name from instructor where Dept_name = NULL;
View Answer

Answer: a
Explanation: Here only the common elements are displayed .

3. Select distinct Dept_name from instructor ;
How many row(s) are displayed ?
a) 4
b) 3
c) 5
d) Error
View Answer

Answer: a
Explanation: Distinct keyword eliminates the the common Dept_name .
Note: Join free Sanfoundry classes at Telegram or Youtube

4. Suppose the Authority want to include a new instructor for the title Neuroscience what command should be inserted ?
a) Insert into instructor values(12111,Emma,NeuroScience,200000);
b) Insert into course values(12111,Introduction,NeuroScience,2);

Insert into instructor values(12111,Emma,Biology,200000);
   Insert into course values(BIO-112,Introduction to Neuro Science,NeuroScience,2);

d) Insert into course values(12111,Emma,NeuroScience,200000);
View Answer

Answer: c
Explanation: The values have to be inserted into both the relations to be intact .

5. If a person all the people in Music department gets fired which of the following has to be performed on the instructor relation ?
a) Delete Dept_name=Music in instructor;
b) Delete from instructor where Dept_name=Music;
c) Remove Dept_name= Music
d) All of the mentioned
View Answer

Answer: b
Explanation: Delete from table_name where condition .


FROM instructor AS T, instructor AS S
WHERE T.salary > S.salary AND S.dept name = ’Comp.Sci.’;

What will be displayed as the value of name for the above query?
a) Hayley
b) Jackson
c) Hayley and Crick
d) Crick
View Answer

Answer: d
Explanation: Only the greatest salary in Comp.Sci dept is selected for the query.


FROM instructor
WHERE salary > SOME (SELECT salary FROM instructor WHERE dept_name = 'Comp.Sci.');

How many rows are selected ?
a) 3
b) 4
c) 2
d) 1
View Answer

Answer: d
Explanation: This displays the names of instructors with salary greater than that of some (at least one) instructor in the Biology department .

8. How will you select the Names whose first letter is E ?

   SELECT Name
   FROM instructor
   WHERE Name LIKE ’A%;


   SELECT Name
   FROM course
   WHERE Name LIKE ’A%;


   SELECT Dept_name
   FROM instructor
   WHERE Name LIKE ’A%;


   SELECT Name
   FROM instructor
   WHERE Dept_name LIKE ’A%;
View Answer
Answer: a
Explanation: % is used to indicate that some characters may appear .

9. Which function is used to find the count of distinct departments?
a) Dist
b) Distinct
c) Count
d) Count,Dist
View Answer

Answer: a
Explanation: Count (distinct ID) is the correct usage.

10. Which function is used to identify the title with Least scope?
a) Min(Credits)
b) Max(Credits)
c) Min(title)
d) Min(Salary)
View Answer

Answer: a
Explanation: Max is used to find the highest element and Min is used to find the lowest element.

Sanfoundry Global Education & Learning Series – Database Management System.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

Subscribe to our Newsletters (Subject-wise). Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!

Youtube | Telegram | LinkedIn | Instagram | Facebook | Twitter | Pinterest
Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

Subscribe to his free Masterclasses at Youtube & discussions at Telegram SanfoundryClasses.