Query to align data together

Question

Hello All
I have 3 tables say A, B, C
Each contain a column called ID
The number of rows in each table can vary.
I want the output to be like this, so that it aligns the same ids from the 3 tables
in the same row.
Wherever the Id is not present in the table it should be replaced by X
A.ID B.ID C.ID
1 1 X
2 X 2
3 3 X
4 4 X
5 X 5
6 6 6
X 7 X
X 8 X
X X 9
Thanks
Acchu

Answer 1

Solution 1
Outer joining combined with union
select nvl(to_char(a_id), 'X') aId
     , nvl(to_char(b_id), 'X') bId
     , nvl(to_char(c_id), 'X') cId
  from (select a.id a_id
             , b.id b_id
             , c.id c_id
          from table_a a
             , table_b b
             , table_c c
         where b.id = a.id(+)
           and b.id = c.id(+)
        union
        select a.id
             , b.id
             , c.id
          from table_a a
             , table_b b
             , table_c c
         where a.id = b.id(+)
           and a.id = c.id(+)
        union
        select a.id
             , b.id
             , c.id
          from table_a a
             , table_b b
             , table_c c
         where c.id = b.id(+)
           and c.id = a.id(+))
order by nvl(b_id, nvl(a_id, c_id))Solution 2
A quick and dirty solution which will work as long as
1) the id's of table_a, table_b and table_c are integers
2) the highest id is lower than the number of rows in the user_objects table
select nvl(to_char(a.id), 'X') a_id
     , nvl(to_char(b.id), 'X') b_id
     , nvl(to_char(c.id), 'X') c_id
  from table_a a
     , table_b b
     , table_c c
     , (select rownum fake_id
          from user_objects) obj
where obj.fake_id = a.id(+)
   and obj.fake_id = b.id(+)
   and obj.fake_id = c.id(+)
   and (a.id is not null
        or
        b.id is not null
        or
        c.id is not null)