递归：
select *
from t_pams_solution t
start with t.id is null
connect by prior id = t.parent_id
order by level desc
红字部分分别为 表名，开始条件，子节点与根关联条件
反递归：
select rownum num,
level lev,
connect_by_root(id) id,
connect_by_root(solution_name) name
from t_pams_solution t
where t.id = 23379
start with 1 = 1
connect by prior id = t.parent_id
order by level desc
红字部分分别为 表名，开始条件，子节点与根关联条件
自动补全查询：
select level from dual
connect by level <10
