asignar un valor en un select oracle

In Oracle SQL Developer

begin
declare v_max number;
   BEGIN
     select max(id_lote) into v_max from cp_lotes;
     DBMS_OUTPUT.PUT_LINE('v_max=' || v_max);
   EXCEPTION
     WHEN NO_DATA_FOUND THEN
       v_max := NULL;
   END;
end;

1. Show the DBMS Output window (View->DBMS Output).
2. Press the "+" button at the top of the Dbms Output window and then select an open database connection in the dialog that opens.