The original operators
Restrict:returns a relation containing all tuples from a specified relation that satisfy a specified condition.
Project: returns a relation containing all (sub)tuples that remain in a specified relation after specified attributes have been removed.
Product: returns relation containing all possible tuples that are a combination of two tuples, one from each of two specified relations.
Union: return a relation containing all tuples that appear in either or both of two specified relations.
Intersect: returns a relation containing all tuples that appear in both of two specified relations.
Difference: returns a relation containing all tuples that appear in the first and not the secondof two specified relations.
Join: return a relation containing all possible tuples that are a combination of two tuples, one from each of two specified relations, such that the two tuples contributing to any given combination have a common value for the common attributes of the two relations.
Divide: Takes two unary relations and one binary relation and returns a relation containing all tuples from on unary relation that appear in the binary relation matched with all tuples in the other tuples in the other unary relation.