Question

I have a table with the following structure:

CHILD_ID | PARENT_ID

Both columns are integers.

I am trying to get all ancestors for a given ‘node’. I have the top most id and I would like to select a table containing all the ids of the children.

CHILD_ID | PARENT_ID
1          2
6          12
2          3
3          4
9          82

Finding the ancestors for 4

Should return

ID
3
2
1

How would this be done in oracle?

Can it be done without a stored procedure?

As always, thank you in advanced for your time.

Answer 1

To meet your output expectations, the query could be like this:

-- sample of data
SQL> with t1(CHILD_ID, PARENT_ID) as(
  2    select 1,  2  from dual union all
  3    select 6,  12 from dual union all
  4    select 2,  3  from dual union all
  5    select 3,  4  from dual union all
  6    select 9,  82 from dual
  7  ) -- actual query
  8  select child_id
  9    from t1
 10  start with parent_id = 4
 11  connect by parent_id = prior child_id
 12  ;

  CHILD_ID
----------
         3
         2
         1