CTE

1.

with treeText(t_name,id,parent_id)
as
(
select t_name,id,parent_id from tree where t_name='A'
union all select t.t_name,t.id,t.parent_id from tree t,treeText tr
where t.parent_id=tr.id
)
select * from treeText order by parent_id

 

2.

with treeText(t_name,id,parent_id)
as
(
select t_name,id,parent_id from tree where t_name='A'
union all select t.t_name,t.id,t.parent_id from tree t
inner join treeText tr on t.parent_id=tr.id
)
select * from treeText order by parent_id