| Selection σc1 Λ c2 Λ …cn(R ): It selects the instances of R that satisfy c1 Λ c2 Λ ...cn Projection πa1 (R ): It returns the attribute a1 Cross product R  S: it return the combination of instances in R and S |
Última modificación: Saturday, 19 de November de 2005, 09:48