Week 01 Lecture (33)

33

Relational Algebra Operations

Selection

σ_C(r) = Sel[C](r) = { t | t ∈ r ∧ C(t) }
C is a boolean function that tests selection condition

Computational view:

result = {}
for each tuple t in relation r
    if (C(t)) { result = result ∪ {t} }