SQL> set null "-"
SQL> /

        ID A B  C
---------- - -- --
         1 a -  -
         1 b -  -
         1 c -  -
         1 - d  -
         1 - e  z
         1 - -  f
         1 - -  g
         1 - -  h
         1 - -  i
         2 a -  -
         2 b -  -
         2 - c  -
         2 - d  -
         2 - -  e

14 rows selected.
SQL> ed
Wrote file afiedt.buf

  1  with s1 as(
  2  select 1 id,       'a' a,  cast(null as varchar2(2)) b,     cast(null as varchar2(2)) c from dual union all
  3  select 1,  'b',    null,   null from dual union all
  4  select 1,  'c',    null,   null from dual union all
  5  select 1,  null,   'd',    null from dual union all
  6  select 1,  null,   'e',    'z' from dual union all
  7  select 1,  null,   null,   'f' from dual union all
  8  select 1,  null,   null,   'g' from dual union all
  9  select 1,  null,   null,   'h' from dual union all
 10  select 1,  null,   null,   'i' from dual union all
 11  select 2,  'a',    null,   null from dual union all
 12  select 2,  'b',    null,   null from dual union all
 13  select 2,  null,   'c',    null from dual union all
 14  select 2,  null,   'd',    null from dual union all
 15  select 2,  null,   null,   'e'  from dual),
 16  s2 as (
 17  SELECT
 18     tt.*
 19    ,row_number() over (partition by id,f order by t) rn FROM s1
 20  UNPIVOT (t FOR f IN (a AS 'a',b AS 'b',c AS 'c')) tt
 21  )
 22  select * from s2
 23  pivot (max(t) for f in ('a' a,'b' b,'c' c))
 24* order by 1,2
 25  /

        ID         RN A  B  C
---------- ---------- -- -- --
         1          1 a  d  f
         1          2 b  e  g
         1          3 c  -  h
         1          4 -  -  i
         1          5 -  -  z
         2          1 a  c  e
         2          2 b  d  -

7 rows selected.

SQL>