Oracle递归查询层级及路径

一、建表及插入数据

ocation_id	location_name	parent_location_id
1	广东省	NULL
2	广州市	1
3	深圳市	1
4	天河区	2
5	番禺区	2
6	南山区	3
7	宝安区	3

建表sql：

CREATE TABLE locations (location_id NUMBER PRIMARY KEY,location_name VARCHAR2(100),parent_location_id NUMBER
);
INSERT INTO locations (location_id, location_name, parent_location_id)
VALUES (1, '广东省', NULL);INSERT INTO locations (location_id, location_name, parent_location_id)
VALUES (2, '广州市', 1);INSERT INTO locations (location_id, location_name, parent_location_id)
VALUES (3, '深圳市', 1);INSERT INTO locations (location_id, location_name, parent_location_id)
VALUES (4, '天河区', 2);INSERT INTO locations (location_id, location_name, parent_location_id)
VALUES (5, '番禺区', 2);INSERT INTO locations (location_id, location_name, parent_location_id)
VALUES (6, '南山区', 3);INSERT INTO locations (location_id, location_name, parent_location_id)
VALUES (7, '宝安区', 3);

二、展现出省市县之间的层级结构

sql：

SELECT location_id, location_name, LEVEL
FROM locations
CONNECT BY PRIOR location_id = parent_location_id
START WITH parent_location_id IS NULL;

结果：

location_id	location_name	LEVEL
1	广东省	1
2	广州市	2
4	天河区	3
5	番禺区	3
3	深圳市	2
6	南山区	3
7	宝安区	3

三、每个区域在层级结构中的完整路径

sql：

SELECT location_id, location_name, LEVEL, SYS_CONNECT_BY_PATH(location_name,'/') AS path
FROM locations
CONNECT BY PRIOR location_id = parent_location_id
START WITH parent_location_id IS NULL;

结果：

location_id	location_name	LEVEL	path
1	广东省	1	广东省
2	广州市	2	广东省/广州市
4	天河区	3	广东省/广州市/天河区
5	番禺区	3	广东省/广州市/番禺区
3	深圳市	2	广东省/深圳市
6	南山区	3	广东省/深圳市/南山区
7	宝安区	3	广东省/深圳市/宝安区