Relational Algebra

The original operators

Restrict: returns a relation containing all tuples from a specified relation that satisfya specified condition. 

Project: returns a relation containing all (sub)tuples that remain in a specified relation afterspecified 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 ineither or both of two specified relations. 

Intersect: returns a relation containing all tuples that appear inboth of two specified relations.

Difference: returns a relation containing all tuples that appear in the first and not the second of 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.