Hi Francesco, i'm answering you late because sometimes i cant connect so frecuently to internet.
if you want to have 'SMITHJOHN' in Oracle you must use the concat function in oracle, it replace the + in VFP
Example: SELECT CONCAT(last_name, firstname) as col1 FROM mytab WHERE concat(last_name,firstname)='SMITHJOHN';
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XXLastnameXXFirstname ('SMITHJOHN')