oracle树形查询

查询一个树的所以叶子节点：

方法1：

select 'A',id,s_id, level from test
where connect_by_isleaf =1  //叶子节点
start with id = 'A' 
connect by prior s_id = id



//方法2：

select 'A', a.s_id from 
(
select * from test
start with id = 'A' 
connect by prior s_id = id
) a where not exists (select 1 from test t1 where t1.id = a.s_id )