Oracle遞迴查詢簡單範例

2022-11-11 14:02:19

1 資料準備

create table area_test(
  id         number(10) not null,
  parent_id  number(10),
  name       varchar2(255) not null
);

alter table area_test add (constraint district_pk primary key (id));

insert into area_test (ID, PARENT_ID, NAME) values (1, null, '中國');
insert into area_test (ID, PARENT_ID, NAME) values (11, 1, '河南省'); 
insert into area_test (ID, PARENT_ID, NAME) values (12, 1, '北京市');
insert into area_test (ID, PARENT_ID, NAME) values (111, 11, '鄭州市');
insert into area_test (ID, PARENT_ID, NAME) values (112, 11, '平頂山市');
insert into area_test (ID, PARENT_ID, NAME) values (113, 11, '洛陽市');
insert into area_test (ID, PARENT_ID, NAME) values (114, 11, '新鄉市');
insert into area_test (ID, PARENT_ID, NAME) values (115, 11, '南陽市');
insert into area_test (ID, PARENT_ID, NAME) values (121, 12, '朝陽區');
insert into area_test (ID, PARENT_ID, NAME) values (122, 12, '昌平區');
insert into area_test (ID, PARENT_ID, NAME) values (1111, 111, '二七區');
insert into area_test (ID, PARENT_ID, NAME) values (1112, 111, '中原區');
insert into area_test (ID, PARENT_ID, NAME) values (1113, 111, '新鄭市');
insert into area_test (ID, PARENT_ID, NAME) values (1114, 111, '經開區');
insert into area_test (ID, PARENT_ID, NAME) values (1115, 111, '金水區');
insert into area_test (ID, PARENT_ID, NAME) values (1121, 112, '湛河區');
insert into area_test (ID, PARENT_ID, NAME) values (1122, 112, '舞鋼市');
insert into area_test (ID, PARENT_ID, NAME) values (1123, 112, '寶丰市');
insert into area_test (ID, PARENT_ID, NAME) values (11221, 1122, '尚店鎮');

2 start with connect by prior遞迴查詢

2.1 查詢所有子節點

select *
from area_test
start with name ='鄭州市'
connect by prior id=parent_id

2.2 查詢所有父節點

select t.*,level
from area_test t
start with name ='鄭州市'
connect by prior t.parent_id=t.id
order by level asc;

start with 子句：遍歷起始條件，如果要查父結點，這裡可以用子結點的列，反之亦然。
connect by 子句：連線條件。prior 跟父節點列parentid放在一起，就是往父結點方向遍歷；prior 跟子結點列subid放在一起，則往葉子結點方向遍歷。parent_id、id兩列誰放在“=”前都無所謂，關鍵是prior跟誰在一起。
order by 子句：排序。

2.3 查詢指定節點的，根節點

select d.*,
	   connect_by_root(d.id) rootid,
	   connect_by_root(d.name) rootname
from area_test d
where name='二七區'
start with d.parent_id IS NULL
connect by prior d.id=d.parent_id

2.4 查詢巴中市下行政組織遞迴路徑

select id, parent_id, name, sys_connect_by_path(name, '->') namepath, level
from area_test
start with name = '平頂山市'
connect by prior id = parent_id

3 with遞迴查詢

3.1 with遞迴子類

with tmp(id, parent_id, name) 
as (
	select id, parent_id, name
    from area_test
    where name = '平頂山市'
    union all
    select d.id, d.parent_id, d.name
    from tmp, area_test d
    where tmp.id = d.parent_id
   )
select * from tmp;

3.2 遞迴父類別

with tmp(id, parent_id, name) 
as
  (
   select id, parent_id, name
   from area_test
   where name = '二七區'
   union all
   select d.id, d.parent_id, d.name
   from tmp, area_test d
   where tmp.parent_id = d.id
   )
select * from tmp;

補充：範例

我們稱表中的資料存在父子關係，通過列與列來關聯的，這樣的資料結構為樹結構。

現在有一個menu表，欄位有id，pid，title三個。

查詢選單id為10的所有子選單。

SELECT * FROM tb_menu m START WITH m.id=10 CONNECT BY m.pid=PRIOR m.id;

將PRIOR關鍵字放在m.id前面，意思就是查詢pid是當前記錄id的記錄，如此順延找到所有子節點。

查詢選單id為40的所有父選單。

SELECT * FROM tb_menu m START WITH m.id=40 CONNECT BY PRIOR m.pid= m.id ORDER BY ID;

總結

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