SQL> with tb as(
  2       select '2001' dt1,10 num1,'2003' dt2,3 num2 from dual union all
  3       select '2004',3,'2000',5 from dual union all
  4       select '2003',5,'2001',2 from dual)
  5  select nvl(a.dt1,b.dt2) dt,nvl(a.num1,0),nvl(b.num2,0)
  6    from tb a full join tb b
  7      on a.dt1=b.dt2
  8   order by dt
  9  /
 
DT   NVL(A.NUM1,0) NVL(B.NUM2,0)
---- ------------- -------------
2000             0             5
2001            10             2
2003             5             3
2004             3             0