oracle关于树形节点处理

create table automobiles(
       part_id number(5) constraint pk_auto_part_id primary key,
       parent_id number(5) constraint fk_auto_ppid_ references  automobiles(part_id),
       part_cname varchar2(30) not null,
       part_ename varchar2(30) not null,
       mp_cost number(9,2),
       desribe varchar2(20)    
);
--插入数据
insert into automobiles values( 1,1,'汽车','mobile',84321.99,'Assembly');
insert into automobiles values( 2,1,'车身','bodywork',19892.99,'Manufacture');
insert into automobiles values( 3,1,'发送机','engine',42128,'Purchase');
insert into automobiles values( 4,1,'附件','attached',15212,'Assembly');
insert into automobiles values( 5,2,'保险杠','bumper',4812.95,'Purchase');
insert into automobiles values( 6,2,'底盘','chassis',12795.11,'Manufacture');
insert into automobiles values( 7,2,'行李箱','Boot',812.11,'Manufacture');
insert into automobiles values( 8,6,'车轮','Wheel',2062.2,'Manufacture');
insert into automobiles values( 9,6,'挡泥板','Mudguard',990,'Manufacture');
insert into automobiles values( 10,8,'轮胎','Tyre',300,'Purchase');
insert into automobiles values( 11,3,'发送机盘','Bonnet',3212,'Manufacture');
insert into automobiles values( 12,3,'活塞','Piston',1112.2,'Manufacture');
insert into automobiles values( 13,3,'汽化器','Carburetter',712.29,'Manufacture');
insert into automobiles values( 14,4,'变速器','Gearbox',5712.25,'Manufacture');
insert into automobiles values( 15,4,'仪表板','Dashboard',538.92,'Manufacture');
insert into automobiles values( 16,14,'制动器','Carburetter',712.29,'Manufacture');
insert into automobiles values( 17,14,'变速杆','Gearshift',2001,'Manufacture');
insert into automobiles values( 18,17,'传动轴','Shaft',1101,'Manufacture');
insert into automobiles values( 19,15,'里程表','Milometer',350.28,'Purchase');
--分层显示当一级目录的父节点不为空时容易出现loop循环找parent_id就找不到了
--解决办法加上nocycle就可以了，或者把你的数据1,1--〉改为1,null
select level,part_id,parent_id,part_cname,part_ename,mp_cost,desribe
from automobiles
start with part_id=1
connect by nocycle prior part_id=parent_id
order by level;
--缩进显示节点
select level,
    lpad('  ',2*level-1)||part_cname||' '||part_ename as partName
from automobiles
start with part_id=1
connect by nocycle prior part_id=parent_id
order by level;