create table bicycle
(
part_id number(5) ,
parent_id number(5) constraint fk_bicycle_pid references bicycle(part_id),
part_name varchar2(30) not null,
mp_cost number(9,2),
describe varchar2(30),
constraint pk_bicycle_part_id primary key (part_id)
);
insert into bicycle values(1,null,自行车，379.组装；
insert into bicycle values101.制造；
insert into bicycle values159.制造；
insert into bicycle values118.制造与采购；
insert into bicycle values(5，2，车把，37.制造；
insert into bicycle values前叉，24.制造；
insert into bicycle values19..制造；
insert into bicycle values19..制造；
insert into bicycle values前轴棍，8，.制造；
insert into bicycle values四、七、前轴身.制造；
insert into bicycle values(11，7，前轴碗，6.制造；
insert into bicycle values12、10、前轴管.制造；
insert into bicycle values(13，10，前轴盘，3.制造；
select
,t.* from bicycle t
t.part_id=1
part_id=parent_id
order by level;
查询包括子孙的所有直属节点；
select ,t.* from bicycle t t.part_id=1 part_id= parent_id
order by level;
假如找的是节点的直属父节点，也不需要树型查询。