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Relational Algebra Operations (cont)

Set operations involve two relations r(R), s(R)   (union-compatible)

Union

  • r1 ∪ r2   =   { t  |  t ∈ r1 ∨ t ∈ r2 },     where r1(R), r2(R)
Computational view: 

result = r1
for each tuple t in relation r2
    result = result ∪ {t}