declare
    object_exists exception;
	except_00957  exception;
	
    pragma exception_init (object_exists , -01430);
    pragma exception_init (except_00957 , -00957);
begin
	execute immediate 'ALTER TABLE DESCONTO_COMISSAO RENAME COLUMN PRECO TO PRECO_OLD';	
	
    exception 
	  when object_exists then null;
	  when except_00957 then null;
end;