SQL & PL/SQL

Hi,
I have 2 tables:

Select group_id from address_group;

group_id
--------
1
2
3
4
5

Select group_id,address_id,group_flag from address;

group_id address_id group_flag
-------- ---------- ----------
1 2 Y
1 3 Y
1 100 N
1 500 N
2 4 Y
2 200 N
2 300 N
3 100 N
3 7 N
3 400 N
4 500 N

The group_flag marks an address_id as being a group_id(parent address_id)

I need a select statement that will return all non-group address_ids(children,grandchildren,etc) for each group_id.

group_id address_id group_flag
-------- ---------- ----------
1 500 N
1 200 N
1 300 N
1 100 N
1 7 N
1 400 N
1 100 N
1 500 N
2 500 N
2 200 N
2 300 N
3 100 N
3 7 N
3 400 N
4 500 N

In fact I don't need last column(group_flag), I used it to show that the final result set contains only non-group address_ids.

Thank you,

Monica