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Placement Preparation Questions
Placement Preparation questions are free resources offered by mobiprep that can help you ace any company placement process. We have curated a list of the most important MCQ questions which are asked in most companies such as Infosys, TCS, Wipro, Accenture, etc. The placement preparation questions also have detailed explanations for every question ensuring you revise all the questions with detailed answers and explanations.
Q
31
The steps in designing a database are:
a.
Logical model 🡪 conceptual model 🡪 physical model
b.
Logical model 🡪 physical model 🡪 conceptual model
c.
Physical model 🡪 conceptual model 🡪 logical model
d.
Conceptual model 🡪 logical model 🡪 physical model
Correct Answer & Explanation:
d
The conceptual design is done first in the database modeling. After conceptual design, the logical design which involves designing of tables is done. At last, the physical design is done.
Q
32
Find the 3NF relations of the given relation Student (rollno, name, phone, year, course id, course max)
a.
student (rollno, name, year, phone)
course (course id, course max)
b.
student ( rollno, name, year, phone)
students (rollno, course id)
course (course id, course max)
c.
student (rollno , name, phone)
year (rollno, year)
course (course id, course max)
d.
student (rollno, name, phone)
course (course id, course max, year)
Correct Answer & Explanation:
b
A relation can be converted to 3NF by moving all the items which are involved in transitive dependency. Hence, the correct answer is option b)
Q
33
The given SQL statement performs which type of join? SELECT Name, Amount, Order_id FROM Customer, Order
a.
Cartesian join
b.
Outer join
c.
Inner join
d.
Natural join
Correct Answer & Explanation:
a
If no join is mentioned in the SQL query, Cartesian product is performed. Cartesian join returns the product of all the tuples in Customer and Order relations.
Q
34
What are the operations done by the SQL query given below? SELECT First Name, Last Name, Department_name FROM Emp e, Department d WHERE e.dept_id = d.dept_id
a.
Selection, intersection, join
b.
Selection, projection, join
c.
Difference, projection, join
d.
Intersection, projection, join
Correct Answer & Explanation:
b
In the given SQL query, selection, projection and join operations are performed.
Q
35
Select the unary operation from the following.
a.
Projection
b.
Selection
c.
Generalized selection
d.
Join
Correct Answer & Explanation:
c
As the Generalized selection takes only one argument, it is a unary operator.
Q
36
Which of the following is an example of self-join?
a.
SELECT column
FROM table1 t, table1 s
WHERE condition
b.
SELECT column
FROM table1 t, table2 t
WHERE condition
c.
SELECT column
FROM table1 t
WHERE condition
d.
None of the above
Correct Answer & Explanation:
a
A table joining with itself is called self-join. In option a) the table1 is joined with table1, so it is an example of self-join.
Q
37
Which SQL statement is used to change the definition of a table?
a.
SELECT
b.
UPDATE
c.
ALTER
d.
CREATE
Correct Answer & Explanation:
c
The definition of the table can be changed using DML statements. ALTER is the DML statement which can be used to add, delete and modify the columns of a table. It can also be used to add or drop certain constraints on a table. Hence, the SQL statement used to change the definition of a table is ALTER.
Q
38
Which of the following operators is used to check the existence of any record in a subquery?
a.
EXISTS
b.
IS NULL
c.
NOT NULL
d.
NOT
Correct Answer & Explanation:
a
The EXISTS operator is used to test the existence of records in a subquery. IS NULL operator is used to look for the NULL values in the attributes. NOT is used to negate the output.