with t as

[zabotin]

with
2 data as
3 (select null m#, 1 n# from dual union all
4 select null, 5 from dual union all
5 select null, 3 from dual union all
6 select 1, 2 from dual union all
7 select 2, 4 from dual)
8 select
9 *
10 from
11 data
12 order by
13 1, 2;