Oracle 递归查询详解
来源：程序员人生 发布时间：2015-02-27 07:53:43 阅读次数：4618次
创建表和主外键
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)
);
插入数据
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, '山东省');
insert into A_DISTRICT (id, parent_id, name) values (3, 1, '郑州市');
insert into A_DISTRICT (id, parent_id, name) values (4, 1, '开封市');
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, '中原区');
insert into A_DISTRICT (id, parent_id, name) values (7, 3, '金水区');
insert into A_DISTRICT (id, parent_id, name) values (8, 3, '27区');
insert into A_DISTRICT (id, parent_id, name) values (9, 3, '城管回族区');
insert into A_DISTRICT (id, parent_id, name) values (10, 3, '上街区');
insert into A_DISTRICT (id, parent_id, name) values (11, 3, '惠济区');
insert into A_DISTRICT (id, parent_id, name) values (12, 4, '开封县');
insert into A_DISTRICT (id, parent_id, name) values (13, 4, '杞县');
insert into A_DISTRICT (id, parent_id, name) values (14, 4, '兰考县');
insert into A_DISTRICT (id, parent_id, name) values (15, 4, '通许县');
insert into A_DISTRICT (id, parent_id, name) values (16, 13, '城关镇');
insert into A_DISTRICT (id, parent_id, name) values (17, 13, '5里河镇');
insert into A_DISTRICT (id, parent_id, name) values (18, 13, '邢口镇');
insert into A_DISTRICT (id, parent_id, name) values (19, 13, '柿园乡');
insert into A_DISTRICT (id, parent_id, name) values (20, 13, '城郊乡');
生成数据以下
递归语法和主要使用函数
select * from 表 start with 条件入口 connect by prior id = parent_id（向下）
select * from 表 start with 条件入口 connect by prior parent_id = id（向上）
如果不写prior，表明前序遍历 未指明遍历方向，所以不进行递归，习惯上会在语句后面加上order by排序和group by分组
connect_by_root(列名) 查询根节点
connect_by_isleaf 查询是不是叶子节点，0是，1不是
sys_connect_by_path 查询递归路径
实战
查询根节点
select id, parent_id, name from a_district start with parent_id is null connect by id = parent_id order by id
递归查询 杞县 的所有上级节点（包括当前节点）
select id, parent_id, name from a_district start with name='杞县' connect by prior parent_id = id order by id
递归查询 杞县 的所有上级节点（包括当前节点和根节点）
select id, parent_id, name,connect_by_root(id) city_id, connect_by_root(name) city_name from a_district
start with name='杞县' connect by prior parent_id = id order by id
递归查询 杞县 的所有子城镇乡（包括当前节点）
select id, parent_id, name from a_district start with name='杞县' connect by prior id = parent_id order by id
递归查询 开封市 的所有城镇乡（包括当前节点和根节点）
select id, parent_id, name, connect_by_root(id) city_id, connect_by_root(name) city_name from a_district
start with name='开封市' connect by prior id = parent_id order by id
上行递归查询 城郊乡 深度、是不是包括叶子节点
select id, name, parent_id, level, connect_by_isleaf isleaf from a_district start with name = '城郊乡' connect by prior parent_id = id order by id
下行递归查询 河南省 深度、是不是包括叶子节点
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
上行递归查询 杞县 路径
select id, name, parent_id, substr(sys_connect_by_path(name,'->'),3) name_path from a_district
start with name='杞县' connect by prior parent_id = id order by id
下行递归查询 河南省 路径
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
综合使用
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函数
在
Oracle中，SYS_CONNECT_BY_PATH函数主要作用是可以把1个父节点下的所有子节点通过某个字符进行辨别，然后连接在1个列中显示。
sys_connect_by_path(字段名, 2个字段之间的连接符号)，注意这里的连接符号不要使用逗号，oracle会报错，如果1定要用，可使用replace替换1下，REPLACE(字段名,原字符,',')。
还有，这个函数使用之前必须先建立1个树，否则无用。
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