create table T1 (I int, PARENT_I int, RELATE varchar2(100))

create table T2 (RELATE_STRING varchar2(1000))

insert into T1 values (1, null, 'root')

insert into T1 values (2, 1, 'child')

insert into T1 values (3, 1, 'child')

insert into T1 values (4, 2, 'grandchild')

insert into T1 values (5, 2, 'grandchild')

insert into T1 values (6, 3, 'grandchild')

insert into T1 values (7, 3, 'grandchild')

insert into T1 values (8, 7, 'great grandchild')

commit

insert into T2@don (RELATE_STRING) 
select sys_connect_by_path(RELATE, '-') as RELATE 
from T1@don 
start with PARENT_I is null 
connect by prior I = PARENT_I

select * from T2@don

rollback

insert into T2@don (RELATE_STRING) 
with cte (LVL, I, PARENT_I, RELATE) as ( 
select 1 as LVL, 
    I, 
    PARENT_I, 
    '+' || RELATE as RELATE 
from T1@don 
    where PARENT_I is null 
union all 
select c.LVL + 1, 
    t.I, 
    t.PARENT_I, 
    c.RELATE || '+' || t.RELATE 
from cte c 
join T1 t 
    on t.PARENT_I = c.I) 
select RELATE from cte order by LVL, I

select * from T2@don

rollback

insert into T2 (RELATE_STRING) 
with cte (LVL, I, PARENT_I, RELATE) as ( 
select 1 as LVL, 
    I, 
    PARENT_I, 
    '=' || RELATE as RELATE 
from T1@don 
    where PARENT_I is null 
union all 
select c.LVL + 1, 
    t.I, 
    t.PARENT_I, 
    c.RELATE || '=' || t.RELATE 
from cte c 
join T1 t 
    on t.PARENT_I = c.I) 
select RELATE from cte order by LVL, I

select * from T2@don

rollback