Oracle 树形结构遍历代码讲解

create table test (
　　id int ,
　　pid int ,
　　name varchar(10))

　　insert into test values ( 1, 0 ,'n1' );

　　insert into test values ( 2, 1 ,'n12' );

　　insert into test values ( 3, 1 ,'n13' );

　　insert into test values ( 4, 2 ,'n21' );

　　insert into test values ( 5, 2 ,'n22' );

　　insert into test values ( 6, 3 ,'n31' );

　　insert into test values ( 7, 3 ,'n32' );

　　insert into test values ( 8, 4 ,'n211' );

　　insert into test values ( 9, 4 ,'n212' );

select * from test
start with id=7
connect by id = prior pid;

select * from test
start with id=2
connect by prior id = pid;

select id,name ,level from test
where level <=2
start with id =2
connect by prior id = pid;