请用sql语句写一套超市管理系统

好的，以下是一个基本的超市管理系统的SQL语句：

创建表格：

CREATE TABLE products (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(255) NOT NULL,
    price FLOAT NOT NULL,
    stock INT NOT NULL,
    category VARCHAR(255) NOT NULL
);

CREATE TABLE orders (
    id INT AUTO_INCREMENT PRIMARY KEY,
    customer_name VARCHAR(255) NOT NULL,
    date_ordered DATE NOT NULL
);

CREATE TABLE order_items (
    id INT AUTO_INCREMENT PRIMARY KEY,
    order_id INT NOT NULL,
    product_id INT NOT NULL,
    quantity INT NOT NULL,
    FOREIGN KEY (order_id) REFERENCES orders(id),
    FOREIGN KEY (product_id) REFERENCES products(id)
);

添加产品：

INSERT INTO products (name, price, stock, category)
VALUES ('Toothbrush', 1.99, 100, 'Personal Care');

INSERT INTO products (name, price, stock, category)
VALUES ('Shampoo', 4.99, 50, 'Personal Care');

INSERT INTO products (name, price, stock, category)
VALUES ('Bread', 2.49, 75, 'Food');

INSERT INTO products (name, price, stock, category)
VALUES ('Milk', 3.99, 25, 'Food');

查询产品：

SELECT * FROM products;

SELECT name, price, stock FROM products WHERE category = 'Personal Care';

更新产品：

UPDATE products SET stock = 80 WHERE name = 'Bread';

添加订单：

INSERT INTO orders (customer_name, date_ordered)
VALUES ('John Doe', '2021-01-01');

INSERT INTO orders (customer_name, date_ordered)
VALUES ('Jane Smith', '2021-01-02');

添加订单项：

INSERT INTO order_items (order_id, product_id, quantity)
VALUES (1, 3, 2);

INSERT INTO order_items (order_id, product_id, quantity)
VALUES (2, 1, 1);

查询订单：

SELECT * FROM orders;

SELECT order_items.quantity, products.name, products.price
FROM order_items
JOIN products ON order_items.product_id = products.id
WHERE order_items.order_id = 1;

这只是一个简单的例子，实际的超市管理系统可能需要更多的表格和更复杂的查询。