I am just curios about about is that Relational Algebra under (××) cartesian product count as a group ?
Since, let A,B,CA,B,C be three relations (tables)
A×(B×C)=(A×B)×CA×(B×C)=(A×B)×C
But the thing is II don't know if there exist an Identity relation (table) II, such that A×I=AA×I=A and there exist a relation (table) X (which X is inverse relation (table) of A) denote A×X=X×A=IA×X=X×A=I
My guess is that I = ϕϕ which is the empty relation (table) but I am not sure if this holds.
So, is there really exists an II that make the Relational Algebra under (××) cartesian product a group.
