在两个表中标识相同的对

-- 创建 employees 表
CREATE TABLE employees (
    employee_id INT PRIMARY KEY,
    name VARCHAR(100),
    department_id INT
);

-- 创建 departments 表
CREATE TABLE departments (
    department_id INT PRIMARY KEY,
    department_name VARCHAR(100)
);

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

INSERT INTO departments (department_id, department_name) VALUES
(1, 'HR'),
(2, 'Engineering');

-- 使用内连接查询两个表中相同的记录
SELECT e.employee_id, e.name, d.department_name
FROM employees e
INNER JOIN departments d ON e.department_id = d.department_id;

-- 为 department_id 字段创建索引
CREATE INDEX idx_department_id ON employees(department_id);
CREATE INDEX idx_department_id ON departments(department_id);