Child inherit from parents

Question

I am traversing down a tree and need to know how i can have the child inherit properties from a parent if its value is null;
version 10g
example
id, parent_id, type
1, null, A
2, 1, A
3, 2,null
4, null, B
5, 4, null
for ids 3 and 5 i would like the type to be inherited from the partent so id 3 would have type A and id 5 would have type B.
Message was edited by:
user457357

Answer 1

with t as
( select 1 as id , null as parent_id, 'A' as type from dual
  union all select 2, 1, 'A' from dual
  union all select 3, 2,null from dual
  union all select 4, null, 'B' from dual
  union all select 5, 4, null from dual
  union all select 6, 5, null from dual
  union all select 7, 5, 'C' from dual
  union all select 8, 7, null from dual
select t1.id, t1.parent_id,
    ( select max(t2.type) keep (dense_rank last order by level)
      from t t2
      start with t2.id = t1.id
      connect by t2.id = prior t2.parent_id and prior t2.type is null
    ) as type
  from t t1
       ID     PARENT_ID T
        1               A
        2             1 A
        3             2 A
        4               B
        5             4 B
        6             5 B
        7             5 C
        8             7 C
8 rows selected.