create table test_connect_by (
  parent     integer,
  child      integer,
  constraint uq_tcb unique (child)
);

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, 18);