Algebraic Laws
•Laws involving selection:
– s C AND C’(R) = s C(s C’(R)) = s C(R) ∩ s C’(R)
– s C OR C’(R) = s C(R) U s C’(R)
– s C (R      S) = s C (R)      S
•When C involves only attributes of R
– s C (R – S) = s C (R) – S
– s C (R U S) = s C (R) U s C (S)
– s C (R ∩ S)  = s C (R) ∩ S