It is impossible to join tables in Qlikview unless the tables have field names in common. The only way Qlikview can associate tables is on field names. So what you want is impossible. You could create another key field by using the autonumber or autonumberhashXXX functions.
load A, C, D, E, autonumber(A) as %Key
load B, F, G, autonumber(B) as %Key
Table A and B will now be associated on the new %Key field.