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 )