MySQL CTE 通用表达式详解

WITH cte_name (column1, column2, ...)
AS
(
    SELECT column1, column2, ...
    FROM table_name
    WHERE condition
)
SELECT *
FROM cte_name;
​

CREATE TABLE employees (
    emp_id INT,
    emp_name VARCHAR(100),
    dept_id INT,
    salary DECIMAL(10, 2)
);
INSERT INTO employees (emp_id, emp_name, dept_id, salary) VALUES
(1, 'Alice', 1, 5000.00),
(2, 'Bob', 2, 6000.00),
(3, 'Charlie', 1, 5500.00),
(4, 'David', 3, 7000.00),
(5, 'Eve', 2, 6500.00);
​

WITH dept1_employees AS (
    SELECT emp_id, emp_name, salary
    FROM employees
    WHERE dept_id = 1
)
SELECT *
FROM dept1_employees;
​

WITH RECURSIVE cte_name (column1, column2, ...)
AS
(
    -- 锚定成员
    SELECT column1, column2, ...
    FROM table_name
    WHERE condition
    UNION ALL
    -- 递归成员
    SELECT column1, column2, ...
    FROM cte_name
    JOIN table_name ON condition
)
SELECT *
FROM cte_name;
​

CREATE TABLE employees (
    emp_id INT,
    emp_name VARCHAR(100),
    manager_id INT
);
INSERT INTO employees (emp_id, emp_name, manager_id) VALUES
(1, 'Alice', NULL),
(2, 'Bob', 1),
(3, 'Charlie', 2),
(4, 'David', 1),
(5, 'Eve', 3);
​

WITH RECURSIVE subordinates AS (
    -- 锚定成员：Alice本身
    SELECT emp_id, emp_name, manager_id
    FROM employees
    WHERE emp_name = 'Alice'
    UNION ALL
    -- 递归成员：Alice的下属及其下属
    SELECT e.emp_id, e.emp_name, e.manager_id
    FROM employees e
    JOIN subordinates s ON e.manager_id = s.emp_id
)
SELECT *
FROM subordinates;
​