Home » Database » Database miscellaneous » Question

Database miscellaneous

Easy Questions
Moderate Questions

Database

Database miscellaneous
  1. What is the optimized version of the relation algebra expression πA1(πA2 (σF1 (σF2(r)))) , where A1, A2 are sets of attributes in r with A1 ⊂ A2 and F1, F2 are Boolean expressions based on the attributes in r?
    1. πA1( σ(F1∧F2)(r))
    2. πA1( σ(F1∨F2)(r))
    3. πA2( σ(F1∧F2)(r))
    4. πA2( σ(F1∨F2)(r))
Correct Option: A

ΠA1 (ΠA2 (σF1 (σF1 (r))))
= ΠA1 (ΠA2 (σ (F1 ∧ F2)(r)))
∴ A1 ⊂ A2 , final relation will be displaying values for attributes present in set A.
ΠA1 (σ (F1 ∧ F2)(r))


Your comments will be displayed only after manual approval.