建立表和主外來鍵

CREATE TABLE SC_DISTRICT
(
  ID         NUMBER(10)                  NOT NULL,
  PARENT_ID  NUMBER(10),
  NAME       VARCHAR2(255 BYTE)          NOT NULL
);

ALTER TABLE SC_DISTRICT ADD (
  CONSTRAINT SC_DISTRICT_PK
 PRIMARY KEY
 (ID));

ALTER TABLE SC_DISTRICT ADD (
  CONSTRAINT SC_DISTRICT_R01 
 FOREIGN KEY (PARENT_ID) 
 REFERENCES SC_DISTRICT (ID)
);
 

插入資料

insert into A_DISTRICT (id, parent_id, name) values (1, null, '河南省');
insert into A_DISTRICT (id, parent_id, name) values (2, null, '山東省');
insert into A_DISTRICT (id, parent_id, name) values (3, 1, '鄭州市');
insert into A_DISTRICT (id, parent_id, name) values (4, 1, '開封市');
insert into A_DISTRICT (id, parent_id, name) values (5, 1, '商丘市');
insert into A_DISTRICT (id, parent_id, name) values (6, 3, '中原區');
insert into A_DISTRICT (id, parent_id, name) values (7, 3, '金水區');
insert into A_DISTRICT (id, parent_id, name) values (8, 3, '二七區');
insert into A_DISTRICT (id, parent_id, name) values (9, 3, '城管回族區');
insert into A_DISTRICT (id, parent_id, name) values (10, 3, '上街區');
insert into A_DISTRICT (id, parent_id, name) values (11, 3, '惠濟區');
insert into A_DISTRICT (id, parent_id, name) values (12, 4, '開封縣');
insert into A_DISTRICT (id, parent_id, name) values (13, 4, '杞縣');
insert into A_DISTRICT (id, parent_id, name) values (14, 4, '蘭考縣');
insert into A_DISTRICT (id, parent_id, name) values (15, 4, '通許縣');
insert into A_DISTRICT (id, parent_id, name) values (16, 13, '城關鎮');
insert into A_DISTRICT (id, parent_id, name) values (17, 13, '五里河鎮');
insert into A_DISTRICT (id, parent_id, name) values (18, 13, '邢口鎮');
insert into A_DISTRICT (id, parent_id, name) values (19, 13, '柿園鄉');
insert into A_DISTRICT (id, parent_id, name) values (20, 13, '城郊鄉');
 

生成資料如下

遞迴語法和主要使用函式

      select * from 表 start with 條件入口 connect by prior id =  parent_id（向下）

      select * from 表 start with 條件入口 connect by prior parent_id = id（向上）

如果不寫prior，表明前序遍歷 未指明遍歷方向，所以不進行遞迴，習慣上會在語句後面加上order by排序和group by分組

      connect_by_root(列名)  查詢根節點

      connect_by_isleaf   查詢是否葉子節點，0是，1不是

      sys_connect_by_path  查詢遞迴路徑

實戰

查詢根節點

select id, parent_id, name from a_district start with parent_id is null connect by id = parent_id order by id

遞迴查詢 杞縣 的所有上級節點（包含當前節點）

select id, parent_id, name from a_district start with name='杞縣' connect by prior parent_id = id order by id

遞迴查詢 杞縣 的所有上級節點（包含當前節點和根節點）

select id, parent_id, name,connect_by_root(id) city_id, connect_by_root(name) city_name from a_district 
       start with name='杞縣' connect by prior parent_id = id order by id

遞迴查詢 杞縣 的所有子城鎮鄉（包含當前節點）

select id, parent_id, name from a_district start with name='杞縣' connect by prior id = parent_id order by id

遞迴查詢 開封市 的所有城鎮鄉（包含當前節點和根節點）

select id, parent_id, name, connect_by_root(id) city_id, connect_by_root(name) city_name from a_district 
       start with  name='開封市' connect by prior id = parent_id order by id

上行遞迴查詢 城郊鄉 深度、是否包含葉子節點

select id, name, parent_id, level, connect_by_isleaf isleaf from a_district start with name = '城郊鄉' connect by prior parent_id = id order by id

下行遞迴查詢 河南省 深度、是否包含葉子節點

select id, name, parent_id, level, connect_by_isleaf isleaf from a_district start with name = '河南省' connect by prior id = parent_id order by id

上行遞迴查詢 杞縣 路徑

select id, name, parent_id, substr(sys_connect_by_path(name,'->'),3) name_path from a_district 
       start with name='杞縣' connect by prior parent_id = id order by id

下行遞迴查詢 河南省 路徑

select id, name, parent_id, substr(sys_connect_by_path(name,'->'),3) name_path from a_district 
       start with name='河南省' connect by prior id = parent_id order by id

綜合使用

select id, name, parent_id, level, connect_by_isleaf isleaf, substr(sys_connect_by_path(name,'->'),3) name_path from a_district
        start with name='河南省' connect by prior id = parent_id order by id

SYS_CONNECT_BY_PATH函式

        在Oracle中，SYS_CONNECT_BY_PATH函式主要作用是可以把一個父節點下的所有子節點通過某個字元進行區分，然後連線在一個列中顯示。         sys_connect_by_path(欄位名, 2個欄位之間的連線符號)，注意這裡的連線符號不要使用逗號，oracle會報錯，如果一定要用，可以使用replace替換一下，REPLACE(欄位名,原字元,',')。         還有，這個函式使用之前必須先建立一個樹，否則無用。