大神们！求救！oracle树形表查询，如图该怎么做？？

[菜鸟的鸟]

[nayi_224]

with tab1 as (
select 1 id, null pid from dual union all
select 2 id, 1 pid from dual union all
select 3 id, 1 pid from dual union all
select 4 id, 2 pid from dual union all
select 5 id, 2 pid from dual union all
select 6 id, 3 pid from dual union all
select 7 id, 3 pid from dual 
)
select connect_by_root(t1.id),
       id
  from tab1 t1
 where t1.pid is not null
 start with t1.pid is null
connect by prior t1.id = t1.pid

[AT152S]

with作用是什么？

[菜鸟的鸟]

select connect_by_root(t1.id), id from tab1 t1 where t1.pid is not null start with t1.pid in(select id from work) connect by prior t1.id = t1.pid 提示不能在远程数据库使用start with子查询，怎么办