Hi boulevard,
You didnt mention which database you are using. ORACLE support hierarchical relationship with CONNECT BY and PRIOR. But mySQL doesnt support this. You need to write recursion for this. Consider the following table to check how to use connect by.

create table test_connect_by (
  parent     number,
  child      number,
  constraint uq_tcb unique (child)
);
[download]

insert into test_connect_by values ( 5, 2);
insert into test_connect_by values ( 5, 3);
insert into test_connect_by values (18,11);
insert into test_connect_by values (18, 7);
insert into test_connect_by values (17, 9);
insert into test_connect_by values (17, 8);
insert into test_connect_by values (26,13);
insert into test_connect_by values (26, 1);
insert into test_connect_by values (26,12);
insert into test_connect_by values (15,10);
insert into test_connect_by values (15, 5);
insert into test_connect_by values (38,15);
insert into test_connect_by values (38,17);
insert into test_connect_by values (38, 6);
insert into test_connect_by values (null,38);
insert into test_connect_by values (null,26);
insert into test_connect_by values (null,16);
[download]

select lpad(' ',2*(level-1)) || to_char(child) s 
  from test_connect_by 
  start with parent is null
  connect by prior child = parent;
[download]

This query will yield result like this

38
  15
    10
    5
      2
      3
  17
    9
    8
  6
26
  13
  1
  12
16
[download]

- perl_lover