NPTEL Introduction to Database Systems Week 3 Assignment Answers 2024

Join Our WhatsApp Group Join Now
Join Us On Telegram Join Now

NPTEL Introduction to Database Systems Week 3 Assignment Answers 2024

1. Some relations may not have a key.

  • True
  • False
Answer :- For Answer Click Here

2. An attribute name should not be used in more than one relation.

  • True
  • False
Answer :- For Answer Click Here

3. A key of a relation may have more than one attribute.

  • True
  • False
Answer :- For Answer Click Here

4. The elements of the domain of an attribute may be ordered pairs of values.

  • True
  • False
Answer :- 

5. Some relations may not have a foreign key.

  • True
  • False
Answer :- 

6. A foreign key in a relation should consist of exactly one attribute.

  • True
  • False
Answer :- For Answer Click Here

7. A foreign key in a relation R can NOT be used to refer to tuples in R itself.

  • True
  • False
Answer :- 

8. If A is a foreign key in R, no null values are permitted in the column A in any instance of R.

  • True
  • False
Answer :- 

9. Suppose A is a foreign key in R that refers to tuples of S using values of the key attribute B of S. Let X be the set of all non-null values of
column A and let Y be the set of all values of column B. Identify the correct relationship between X and Y that holds in
all instances of R and S:

  • X is a subset of Y
  • X is a proper subset of Y
  • Y is a subset of X
  • X need not be a subset of Y and Y need not be a subset of X
Answer :- 

10. Consider the following relations S1(P,Q,R) and S2(T,U,V) and the given instances. What is the result of the relational algebra expression

NPTEL Introduction to Database Systems Week 3 Assignment Answers 2024
  • Empty relation
  • { (2,4), (3,6) }
  • A relation with scheme (P,Q) and tuples { (1,2) }
  • A relation with scheme (P,Q) and tuples { (1,2), (2,4), (3,6) }
Answer :- For Answer Click Here

11.

Using the relation instances given in the Question 10, find out how many tuples will be there in the result of the following relational algebra expression:

                S1⋈S1.Q≥S2.VS2
  • 20
  • 9
  • 8
  • 16
Answer :- 

12. Consider the four relations R1(A, B, C), R2(X, Y, Z), R3(A, B, D) and R4(U, X, Y). The domains of the attributes are: A – integers;
B – strings; C – single characters; D – { ‘M’, ‘F’ }; U – integers; X – strings; Y – single characters; Z – { ‘M’, ‘F’ }. Identify the
pair of union-compatible relations:

  • Pair R1, R3
  • Pair R1, R4
  • Pair R2, R3
  • Pair R3, R4
Answer :- 

13. The ​ join ​ relational algebra operator can NOT be expressed using other operators.

  • True
  • False
Answer :- 

14. The ​ cross product ​ relational algebra operator requires its operands to be union-compatible.

  • True
  • False
Answer :- For Answer Click Here

15. The ​ difference ​ relational algebra operator requires its operands to be union-compatible.

  • True
  • False
Answer :- 

16. When ​ project ​ is applied on an instance ​ r , ​ the size of the result will always be the same as that of ​ r.

  • True
  • False
Answer :- 

17. Consider the following relations S1(P,Q,R) and S2(P,R) and the given instances. What is the result of the relational algebra expression?

NPTEL Introduction to Database Systems Week 3 Assignment Answers 2024
  • Empty relation
  • A relation with scheme (Q) and tuples { (2), (4) }
  • A relation with scheme (Q) and tuples { (2), (4), (6) }
  • { 2, 4 }
Answer :- 

18. Consider the following relation S1 and its given instance. What is the size of the result of the following relational algebra expression
on the relation S1?

NPTEL Introduction to Database Systems Week 3 Assignment Answers 2024
  • 5
  • 6
  • 7
  • 8
Answer :- For Answer Click Here

19. On the same relation given in Question 18, what is the size of the result of the following relational algebra expression?

NPTEL Introduction to Database Systems Week 3 Assignment Answers 2024
  • 9
  • 10
  • 11
  • 12
Answer :- For Answer Click Here