非常小的“多”表的SQL一对多关系

-- 创建订单表
CREATE TABLE orders (
    order_id INT PRIMARY KEY,
    customer_name VARCHAR(255),
    order_date DATE
);

-- 创建订单项表
CREATE TABLE order_items (
    item_id INT PRIMARY KEY,
    order_id INT,
    product_name VARCHAR(255),
    quantity INT,
    FOREIGN KEY (order_id) REFERENCES orders(order_id)
);

-- 插入订单
INSERT INTO orders (order_id, customer_name, order_date)
VALUES (1, 'John Doe', '2023-04-01');

-- 插入订单项
INSERT INTO order_items (item_id, order_id, product_name, quantity)
VALUES (1, 1, 'Product A', 2);

-- 为order_id创建索引
CREATE INDEX idx_order_id ON order_items(order_id);

-- 优化查询语句
SELECT * FROM orders o JOIN order_items oi ON o.order_id = oi.order_id WHERE o.order_id = 1;