250+ TOP MCQs on Querying database part DML and Answers

Database Questions & Answers on “Querying database part-1 DML”

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;

Answer: c
Clarification: 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;

Answer: a
Clarification: 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

Answer: a
Clarification: Distinct keyword eliminates the the common Dept_name .

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);
c)

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);

Answer: c
Clarification: 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

Answer: b
Clarification: Delete from table_name where condition .

6.

SELECT DISTINCT T.name
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

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

7.

SELECT Name
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

Answer: d
Clarification: 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 ?
a)

   SELECT Name
   FROM instructor
   WHERE Name LIKE ’A%;

b)

   SELECT Name
   FROM course
   WHERE Name LIKE ’A%;

c)

   SELECT Dept_name
   FROM instructor
   WHERE Name LIKE ’A%;

d)

   SELECT Name
   FROM instructor
   WHERE Dept_name LIKE ’A%;

View Answer

Answer: a
Clarification: % 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

Answer: a
Clarification: 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)

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