Oracle递归查询层级及路径

一、建表及插入数据

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：

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：