DBMS Multiple choice Questions and Answers-RDBMS

11.	What action does ⋈ operator perform in relational algebra
a.	Output specified attributes from all rows of the input relation and remove duplicate tuples from the output
b.	Outputs pairs of rows from the two input relations that have the same value on all attributes that have the same name
c.	Output all pairs of rows from the two input relations (regardless of whether or not they have the same values on common attributes)
d.	Return rows of the input relation that satisfy the predicate

Answer: (a).Output specified attributes from all rows of the input relation and remove duplicate tuples from the output

12.	What does the “x” operator do in relational algebra?
a.	Output specified attributes from all rows of the input relation. Remove duplicate tuples from the output
b.	Output pairs of rows from the two input relations that have the same value on all attributes that have the same name
c.	Output all pairs of rows from the two input relations (regardless of whether or not they have the same values on common attributes)
d.	Returns the rows of the input relation that satisfy the predicate

Answer: (c).Output all pairs of rows from the two input relations (regardless of whether or not they have the same values on common attributes)

13.	An attribute is a __________ in a relation.
a.	Row
b.	Column
c.	Value
d.	Tuple

Answer: (b).Column

14.	What is the method of specifying a primary key in a schema description?
a.	By writing it in bold letters
b.	By underlining it using a dashed line
c.	By writing it in capital letters
d.	By underlining it using a bold line

Answer: (d).By underlining it using a bold line

15.	Statement 1: A tuple is a row in a relation Statement 2: Existence of multiple foreign keys in a same relation is possible
a.	Both the statements are true
b.	Statement 1 is correct but Statement 2 is false
c.	Statement 1 is false but Statement 2 is correct
d.	Both the statements are false

Answer: (a).Both the statements are true

16.	Choose the option that correctly explains in words, the function of the following relational algebra expression: σyear≥2009 (book ⋈ borrow)
a.	Selects all tuples from the Cartesian product of book and borrow
b.	Selects all the tuples from the natural join of book and borrow wherever the year is lesser than 2009
c.	Selects all the tuples from the natural join of book and student wherever the year is greater than or equal to 2009
d.	Selects all tuples from the Cartesian product of book and borrow wherever the year is greater than or equal to 2009

Answer: (b).Selects all the tuples from the natural join of book and borrow wherever the year is lesser than 2009

17.	State true or false: If a relation consists of a foreign key, then it is called a referenced relation of the foreign key dependency.
a.	True
b.	False
c.	May be
d.	Can't say

Answer: (b).False

18.	Which of the following is not a feature of a good relational design?
a.	Specifying primary keys
b.	Specifying foreign keys
c.	Preserving integrity constraints
d.	Allowing redundancy of attributes

Answer: (d).Allowing redundancy of attributes

19.	The dependency rules specified by the database designer are known as _______
a.	Designer dependencies
b.	Database rules
c.	Functional dependencies
d.	None of the mentioned

Answer: (c).Functional dependencies

20.	If the decomposition is unable to represent certain important facts about the relation, then such a decomposition is called as?
a.	Lossless decomposition
b.	Lossy decomposition
c.	Insecure decomposition
d.	Secure decomposition

Answer: (b).Lossy decomposition