确保文档中的属性只有在它们与另一个属性具有相同的值时才是唯一的

def create_order(customer_id, product_id):
    # 检查是否存在相同客户和产品的订单
    existing_orders = db.execute(
        "SELECT * FROM orders WHERE customer_id = ? AND product_id = ?",
        (customer_id, product_id)
    )
    if existing_orders:
        raise ValueError("Duplicate order for the same customer and product is not allowed.")
    
    # 插入新订单
    db.execute(
        "INSERT INTO orders (customer_id, product_id) VALUES (?, ?)",
        (customer_id, product_id)
    )

CREATE TRIGGER check_unique_order
BEFORE INSERT ON orders
FOR EACH ROW
BEGIN
    DECLARE duplicate_order INT;
    SELECT COUNT(*) INTO duplicate_order
    FROM orders
    WHERE customer_id = NEW.customer_id AND product_id = NEW.product_id;
    
    IF duplicate_order > 0 THEN
        SIGNAL SQLSTATE '45000'
        SET MESSAGE_TEXT = 'Duplicate order for the same customer and product is not allowed.';
    END IF;
END;