I have the following result.
The idea is the returned result for id2
to apply it in an in clause when that result is in one line and there are 2 ids for it

          select 10 id1,   '100,101' id2   from dual 
          union all
          select 11 id1,   '102,103' id2   from dual 

the result of id2
to be applied in an in clause.