连接两个查询结果

-- 创建用户表
CREATE TABLE users (
    user_id INT PRIMARY KEY,
    username VARCHAR(50),
    email VARCHAR(100)
);

-- 创建订单表
CREATE TABLE orders (
    order_id INT PRIMARY KEY,
    user_id INT,
    product_name VARCHAR(100),
    order_date DATE
);

-- 插入示例数据
INSERT INTO users (user_id, username, email) VALUES
(1, 'Alice', 'alice@example.com'),
(2, 'Bob', 'bob@example.com');

INSERT INTO orders (order_id, user_id, product_name, order_date) VALUES
(101, 1, 'Product A', '2023-01-01'),
(102, 2, 'Product B', '2023-01-02'),
(103, 1, 'Product C', '2023-01-03');

-- 内连接示例
SELECT users.username, orders.product_name, orders.order_date
FROM users
INNER JOIN orders ON users.user_id = orders.user_id;

-- 左连接示例
SELECT users.username, orders.product_name, orders.order_date
FROM users
LEFT JOIN orders ON users.user_id = orders.user_id;

-- 右连接示例
SELECT users.username, orders.product_name, orders.order_date
FROM users
RIGHT JOIN orders ON users.user_id = orders.user_id;

-- 全连接示例
SELECT users.username, orders.product_name, orders.order_date
FROM users
FULL JOIN orders ON users.user_id = orders.user_id;