mysql全连接写法

SELECT *
FROM table1
LEFT JOIN table2 ON table1.id = table2.id
UNION
SELECT *
FROM table1
RIGHT JOIN table2 ON table1.id = table2.id;

-- 创建示例表
CREATE TABLE employees (
    id INT PRIMARY KEY,
    name VARCHAR(100),
    department_id INT
);

CREATE TABLE departments (
    id INT PRIMARY KEY,
    name VARCHAR(100)
);

-- 插入示例数据
INSERT INTO employees (id, name, department_id) VALUES
(1, 'Alice', 1),
(2, 'Bob', NULL),
(3, 'Charlie', 2);

INSERT INTO departments (id, name) VALUES
(1, 'HR'),
(2, 'Engineering');

-- 使用全连接查询
SELECT e.id, e.name AS employee_name, d.name AS department_name
FROM employees e
LEFT JOIN departments d ON e.department_id = d.id
UNION
SELECT e.id, e.name AS employee_name, d.name AS department_name
FROM employees e
RIGHT JOIN departments d ON e.department_id = d.id;