Java优学网MySQL内连接教程：从基础语法到性能优化实战

SELECT 列名1, 列名2, ... FROM 表1 INNER JOIN 表2 ON 表1.列名 = 表2.列名;

SELECT e.employee_name AS '员工姓名',

   m.employee_name AS '经理姓名'

FROM employees e INNER JOIN employees m ON e.manager_id = m.employee_id;

-- 确保连接键上有索引 CREATE INDEX idx_users_user_id ON users(user_id); CREATE INDEX idx_orders_user_id ON orders(user_id);

SELECT u.username, o.order_number FROM users u INNER JOIN orders o ON u.user_id = o.user_id;