NPTEL Introduction to Database Systems Week 4 Assignment Answers 2024

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NPTEL Introduction to Database Systems Week 4 Assignment Answers 2024

1. Consider the statements given below:

S1: Every TRC query is safe.
S2: There can be more than one free variable in a condition of a TRC query.

Choose the correct option:

  • S1: True; S2: True
  • S1: True; S2: False
  • S1: False; S2: False
  • S1: False; S2: True
Answer :- For Answer Click Here 

2. Consider the sets S1 and S2 below. S1 has different types of keys and S2 has possible constraints on the number of such keys in a relation. Choose the correct matching:

S1: {w: primary key; x: candidate key; y: super key; z: foreign key}
S2: { p: zero or more, q: exactly one, r: one or more }

Choose the correct mapping:

  • w–p; x–p; y–q; z–r
  • w–q; x–q; y–p; z–r
  • w–q; x–r; y–r; z–p
  • w–r-; x–r; y–p; z–q
Answer :- For Answer Click Here

3. Consider the statements given below:

S1: If the ​ candidate key ​ consists of ​ n ​ attributes for a relation R, then ​ primary key ​ attribute-set always has less than ​ n ​ attributes for the same relation.

S2: If a relation does not have a ​ candidate key ​ still it can have a ​ primary key ​ .

Choose the correct option:

  • S1: True; S2: True
  • S1: True; S2: False
  • S1: False; S2: False
  • S1: False; S2: True
Answer :- For Answer Click Here

4. Consider the sets mentioned in the table below:

NPTEL Introduction to Database Systems Week 4 Assignment Answers 2024

Choose the correct matching:

  • w–s; x–q ; y–r ; z–p
  • w–s; x–p ; y:–p; z–r
  • w–q; x–r ; y:–r; z–p
  • w–q; x– s; y:–p; z–r
Answer :- 

5. For a relational algebra operator θ , we can rewrite r1θr2 by using other relational algebra operators appropriately. Choose the ​ incorrect​ option:

  • Intersection ​ : the re-written expression requires only ⋃ and −
  • Join ​ : the re-written expression requires only × and σ.
  • Join ​ : the re-written expression requires only II and σ.
  • Division ​ : the re-written expression requires only II,×, and − .
Answer :- 

6. In the tuple relational calculus (TRC) query, one can not give _ _ _ _ of how to evaluate a query. Therefore, we write a _ _ _ _ expression to specify the data retrieval requirement. Fill the blanks:

  • Data; Procedural
  • Description; Procedural
  • Data; Declarative
  • Description; Declarative
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7. Consider the TRC query given below:

NPTEL Introduction to Database Systems Week 4 Assignment Answers 2024
Answer :- 

8. Consider the given relational schemas:

Professor(​ pid​ , pname, age, sex, deptNo, yearOfJoining)
Department(​ did​ , dname, hod, phoneNo)

Choose the appropriate TRC query to retrieve the department names that do not have any female professors:

NPTEL Introduction to Database Systems Week 4 Assignment Answers 2024
Answer :- 
NPTEL Introduction to Database Systems Week 4 Assignment Answers 2024
Answer :- 
NPTEL Introduction to Database Systems Week 4 Assignment Answers 2024
Answer :- For Answer Click Here