Oracle START WITH 递归语句的使用方法

EMPLOYEE_ID | EMPLOYEE_NAME | MANAGER_ID
----------------------------------------
100         | Steven        | NULL
101         | Neena         | 100
102         | Lex           | 100
103         | Alexander     | 102
...         | ...           | ...

SELECT employee_id, employee_name, manager_id
FROM employees
START WITH manager_id IS NULL
CONNECT BY PRIOR employee_id = manager_id;

EMPLOYEE_ID | EMPLOYEE_NAME | MANAGER_ID
----------------------------------------
100         | Steven        | NULL
101         | Neena         | 100
102         | Lex           | 100
103         | Alexander     | 102
...         | ...           | ...

CREATE TABLE EMPLOYEES (
    EMPLOYEE_ID NUMBER PRIMARY KEY,
    EMPLOYEE_NAME VARCHAR2(100),
    MANAGER_ID NUMBER,
    CONSTRAINT fk_manager
    FOREIGN KEY (MANAGER_ID)
    REFERENCES EMPLOYEES (EMPLOYEE_ID)
);

INSERT INTO EMPLOYEES (EMPLOYEE_ID, EMPLOYEE_NAME, MANAGER_ID) VALUES (100, 'Steven', NULL);
INSERT INTO EMPLOYEES (EMPLOYEE_ID, EMPLOYEE_NAME, MANAGER_ID) VALUES (101, 'Neena', 100);
INSERT INTO EMPLOYEES (EMPLOYEE_ID, EMPLOYEE_NAME, MANAGER_ID) VALUES (102, 'Lex', 100);
INSERT INTO EMPLOYEES (EMPLOYEE_ID, EMPLOYEE_NAME, MANAGER_ID) VALUES (103, 'Alexander', 102);
-- 添加更多数据以形成更复杂的层次结构
COMMIT;

SELECT employee_id, employee_name, manager_id
FROM employees
START WITH manager_id IS NULL
CONNECT BY PRIOR employee_id = manager_id
ORDER SIBLINGS BY employee_id;