declare
    type a_type is table of varchar2(10)
     index by pls_integer;
    v_tbl1 a_type;
    v_tbl2 a_type;
begin
    select  ename
      bulk  collect
      into  v_tbl1
      from  emp;
    select  dname
      bulk  collect
      into  v_tbl2
      from dept;
    for v_i in 1..v_tbl2.count loop
      v_tbl1(v_i - v_tbl2.count) := v_tbl2(v_i);
    end loop;
    for v_i in v_tbl1.first..v_tbl1.last loop
      dbms_output.put_line('v_tbl1(' || v_i || ') = ' || v_tbl1(v_i));
    end loop;
end;
/
v_tbl1(-3) = ACCOUNTING
v_tbl1(-2) = RESEARCH
v_tbl1(-1) = SALES
v_tbl1(0) = OPERATIONS
v_tbl1(1) = SMITH
v_tbl1(2) = ALLEN
v_tbl1(3) = WARD
v_tbl1(4) = JONES
v_tbl1(5) = MARTIN
v_tbl1(6) = BLAKE
v_tbl1(7) = CLARK
v_tbl1(8) = SCOTT
v_tbl1(9) = KING
v_tbl1(10) = TURNER
v_tbl1(11) = ADAMS
v_tbl1(12) = JAMES
v_tbl1(13) = FORD
v_tbl1(14) = MILLER

PL/SQL procedure successfully completed.

SQL>

WITH T AS (
           SELECT NULL COL,1 WEIGHT FROM DUAL CONNECT BY LEVEL <= N2_ELEMENT_COUNT
           UNION ALL
           SELECT your_select_list,2 WEIGHT FROM rest_of_your_query
          )
SELECT  COL
  BULK  COLLECT
  INTO  N1
  FROM  T
  ORDER BY WEIGHT;

WITH T AS (
           SELECT NULL COL,1 WEIGHT FROM DUAL CONNECT BY LEVEL <= N1_ELEMENT_COUNT
           UNION ALL
           SELECT your_select_list,2 WEIGHT FROM rest_of_your_query
          )
SELECT  COL
  BULK  COLLECT
  INTO  N
  FROM  T
  ORDER BY WEIGHT;

START WITH N1_ELEMENT_COUNT > 0