mysql关键字pri

CREATE TABLE users (
    user_id INT AUTO_INCREMENT PRIMARY KEY,  -- 单列主键
    username VARCHAR(50) NOT NULL,
    email VARCHAR(100) NOT NULL UNIQUE
);

CREATE TABLE orders (
    order_id INT AUTO_INCREMENT PRIMARY KEY,  -- 单列主键
    user_id INT,
    order_date DATETIME,
    FOREIGN KEY (user_id) REFERENCES users(user_id)
);

CREATE TABLE products (
    product_id INT AUTO_INCREMENT PRIMARY KEY,  -- 单列主键
    product_name VARCHAR(100),
    price DECIMAL(10, 2)
);

CREATE TABLE order_items (
    order_item_id INT AUTO_INCREMENT PRIMARY KEY,  -- 单列主键
    order_id INT,
    product_id INT,
    quantity INT,
    FOREIGN KEY (order_id) REFERENCES orders(order_id),
    FOREIGN KEY (product_id) REFERENCES products(product_id)
);