oracle connect by用法

oracle connect by用法

create table t_location(
id number primary key,
name varchar(16) not null,
pid number not null
)
insert into t_location values(1,'华东区',0);
insert into t_location values(2,'华南区',0);
insert into t_location values(3,'福建省',1);
insert into t_location values(4,'江苏省',1);
insert into t_location values(5,'福州市',3);
insert into t_location values(6,'厦门市',3);
insert into t_location values(7,'苏州市',4);
insert into t_location values(8,'扬州市',4);
insert into t_location values(9,'广东省',2);
insert into t_location values(10,'广西省',2);
insert into t_location values(11,'广州市',9);
insert into t_location values(12,'深圳市',9);
insert into t_location values(13,'南宁市',10);
insert into t_location values(14,'桂林市',10);
--2.1 从根节点查找叶子节点
select t.*, level, CONNECT_BY_ROOT(id)
from t_location t
start with t.id = 1
connect by prior t.id = t.pid;

--2.2 从叶子节点查找上层节点
--第一种,修改prior关键字位置
select t.*, level, CONNECT_BY_ROOT(id)
from t_location t
start with t.id = 14
connect by t.id = prior t.pid;

--第二种,prior关键字不动 调换后面的id=fid逻辑关系的顺序
select t.*, level, CONNECT_BY_ROOT(id)
from t_location t
start with t.id = 14
connect by prior t.pid = t.id;

--查找某个结点的路由
select replace(wm_concat(name),',',' ') as addr from(
select t.name,connect_by_root(id) as rid
from t_location t
start with t.name = '深圳市'
connect by prior t.pid = t.id
order by level desc;
)
--查找所有结点的路由,出现问题,三个结点的,排序错误,出现'华南区 深圳市 广东省'这样的情况
select rid,replace(wm_concat(name),',',' ') as addr from(
select t.name,connect_by_root(id) as rid
from t_location t
connect by prior t.pid = t.id
order by level desc
)
group by rid;