A: Relational Algebra queries for Students, Teachers and Teaches: 63

i. Find the Roll of all students who are taught by teacher "Raman".

π Roll ( σ TName = 'Raman' ( Teaches ⨝ Teachers ) )

 

ii. Delete all students who are from Biratnagar.

Temp1 ← σ SAddress = 'Biratnagar' ( Students )
Students ← Students - Temp1

 

OR

Students ← Students - σ SAddress = 'Biratnagar' ( Students )

 

iii. Increase the fee of students who are from Kathmandu by 2%.

Temp1 ← π Roll, SName, SAddress, SContact, SFee = SFee * 1.02 (σ SAddress = 'Kathmandu' ( Students ))
Temp2 ← σ SAddress ≠ 'Kathmandu' ( Students )
Students ← Temp1 ∪ Temp2

 

OR

Students ← π Roll, SName, SAddress, SContact, SFee = SFee * 1.02 (σ SAddress = 'Kathmandu' ( Students )) ∪ σ SAddress ≠ 'Kathmandu' ( Students )

 

iv. Find the name of teacher who lives in Kathmandu and get salary greater than Rs. 100000.

π TName ( σ TAddress = 'Kathmandu' ^ TSalary > 100000 ( Teachers ) )

 

v. Change the name of student to Sushila whose roll number is 10.

Temp1 ← π Roll, SName = 'Sushila', SAddress, SContact, SFee ( σ Roll = 10 ( Students ) )
Temp2 ← σ Roll ≠ 10 ( Students )
Students ← Temp1 ∪ Temp2

 

OR

Students ← π Roll, SName = 'Sushila', SAddress, SContact, SFee ( σ Roll = 10 ( Students ) ) ∪ σ Roll ≠ 10 ( Students )