Relational Algebra in DBMS

Last Updated :
Discuss
Comments

Question 1

Which relational algebra operation would return only students who play both Badminton and Cricket from STUDENT_SPORTS?

  • σ(SPORTS='Badminton' ∧ SPORTS='Cricket')(STUDENT_SPORTS)

  • ∏ROLL_NO(σ(SPORTS='Badminton')(STUDENT_SPORTS)) ∩ ∏ROLL_NO(σ(SPORTS='Cricket')(STUDENT_SPORTS))

  • ρ(TEMP, σ(SPORTS='Badminton')(STUDENT_SPORTS)) ⋈ σ(SPORTS='Cricket')(STUDENT_SPORTS)

  • STUDENT_SPORTS ÷ SPORTS

Discuss it

Question 2

What is the result of ∏ADDRESS(STUDENT) where STUDENT has duplicate 'DELHI' addresses?

  • Returns all addresses including duplicates

  • Returns only unique addresses

  • Returns an error due to duplicate elimination

  • Returns NULL values for duplicates

Discuss it

Question 3

For relations R(A,B) and S(B,C), which operation requires attribute renaming to avoid ambiguity?

  • R ∪ S

  • R ⋈ S

  • R × S

  • R - S

Discuss it

Question 4

Which operator would find employees who share exact addresses with students?

  • EMPLOYEE ⋈(ADDRESS=ADDRESS) STUDENT

  • ∏ADDRESS(EMPLOYEE) ∩ ∏ADDRESS(STUDENT)

  • σ(EMPLOYEE.ADDRESS=STUDENT.ADDRESS)(EMPLOYEE × STUDENT)

  • EMPLOYEE ÷ STUDENT

Discuss it

Question 5

In the division operation R ÷ S, what condition must hold?

  • Attributes(S) ⊆ Attributes(R)

  • Degree(R) = Degree(S)

  • R and S must be union-compatible

  • |Attributes(R)| > |Attributes(S)|

Discuss it

Question 6

What does R ⟗ S return if R has (1,x) and S has (x,10), (y,20)?

  • (1,x,10)

  • (1,x,10), (NULL,y,20)

  • (1,x,10), (NULL,NULL,NULL)

  • (1,x,NULL), (NULL,y,20)

Discuss it

Question 7

Which operation implements "students who don't play any sports"?

  • STUDENT - STUDENT_SPORTS

  • ∏ROLL_NO(STUDENT) - ∏ROLL_NO(STUDENT_SPORTS)

  • σ(ROLL_NO=NULL)(STUDENT ⋈ STUDENT_SPORTS)

  • STUDENT ÷ STUDENT_SPORTS

Discuss it

Question 8

For R(A,B) with (1,x), (2,y) and S(B) with (x), what is R ÷ S?

  • (1)

  • (1), (2)

  • (x)

  • Empty relation

Discuss it

Question 9

Which relational algebra expression is equivalent to SQL's LEFT JOIN?

  • R ⋈ S

  • R ⟕ S

  • (R × S) ∪ (R × (∏(NULL,...,NULL)(S)))

  • (R ⋈ S) ∪ (R - ∏R.*(R ⋈ S))

Discuss it

Question 10

What distinguishes θ-join from equijoin?

  • θ-join uses only = operator

  • Equijoin eliminates duplicate columns

  • θ-join supports inequality conditions

  • Equijoin requires natural join

Discuss it

There are 10 questions to complete.

Take a part in the ongoing discussion