Rename or (renaming) is a relational operator that rename:
<MATH> \LARGE \rho_{a/b} R </MATH> rename the attribute a from R to b
in SQL, the rename operator is called as
select a as b from R
Rename the 4 attributes {A, B, A, C} resulting from the cross product between R1 and R2 to {A_1, B, A_2, C} <MATH> \LARGE \rho_{A_1,B,A_2,C} \left( \pi_{A,B}R_1 \times \pi_{A,C}R_2 \right) </MATH> where: