Database Management Systems MCQ with answers explained, Multiple choice questions in DBMS with answers, solved interview questions in RDBMS
DBMS Multiple Choice Questions  with Answers
1. Database views
An index is a
special case of virtual view.
a) TRUE
b) FALSE
Answer: (b)
An index is a special case of materialized view, not virtual view. 
2. Normalization
Consider the table
below:
A

B

C

a1

b1

c1

a1

b2

c2

a2

b3

c1

a2

b3

c1

For each of the
functional dependencies listed below, indicate whether it holds or not.
a) C → A, AB → C
b) C → B, AB → C, B
→ C
c) B → A, BC → A, AC → B
d) All of the above
Answer: (c)
C
→ A fails due to the tuples 1, 3, and 4. Hence, option (a) is wrong.
C
→ B fails due to the tuples 1, 3 and 4. Hence, option (b) is wrong.
B
→ A holds in the given relation because B uniquely determines A.
Likewise
BC → A and C → A are also holding in the relation. Hence, option (c) is
correct.

3. Structured Query Language
Consider the following
database schemas and the SQL query;
User
(handle, name, home_city, bio)
Friend
(handle1, handle2)
Message
(handle, text, from_city)
Query: SELECT
handle, bio, min(home_city) FROM User NATURAL JOIN Message GROUP BY handle,
from_city;
What is wrong with
the query?
a) handle
b) bio
c) min(home_city)
d) NATURAL JOIN
Answer: (b)
The
given query performs grouping of records. While using group by function, the
SELECT clause can have either the grouping function or the grouping
attributes. In this query, bio is not one of the grouping attributes. Hence,
bio cannot appear in the SELECT clause of the query.

4. Relation Algebra
Let us suppose that
there two relations R and S. R has 26 rows and 5 columns and S has 30 records
and 3 columns. If Cartesian product operation was carried out on relations R
and S, what would be the degree of the new relation T where T = R X S?
a) 56
b) 15
c) 8
d) 16
Answer: (c)
In relational algebra, the degree of a relation is the number of attributes (columns) that the relation contains.
T
contains 5 columns + 3 columns = 8 columns after Cartesian product operation.

5. Relational Algebra
Use the data from
previous question to answer this question. If Cartesian product operation was
carried out on relations R and S, what would be the cardinality of the new relation T where T = R X S?
a) 8
b) 15
c) 56
d) 780
Answer: (d)
In relational algebra, the cardinality of a relation is the number of tuples (records/rows) that the relation contains.
We
arrived at T after Cartesian product on R and S. Hence, T contains 26 X 30 = 780
rows after Cartesian product operation.

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