Question

我在尝试理解我的表格在数据库中应该如何关联时遇到问题。我是初学者，并试图自己研究。表格如下

    CREATE TABLE PIZZA
(
    pizza_id INT AUTO_INCREMENT PRIMARY KEY,
    pizza_name VARCHAR (255),
    pizza_desc VARCHAR (255),
    pizza_price DOUBLE
);

CREATE TABLE CUSTOMER
(
    cust_id INT AUTO_INCREMENT PRIMARY KEY,
    cust_first_name VARCHAR (255),
    cust_last_name VARCHAR (255),
    cust_street VARCHAR (255),
    cust_apt VARCHAR (255),
    cust_city VARCHAR (255),
    cust_state CHAR(2),
    cust_zip CHAR(5),
    cust_home_phone CHAR(10),
    cust_mobile_phone CHAR(10),
    cust_other_phone CHAR(10)
);

CREATE TABLE PIZZA_ORDER
(
    pizza_order_id INT AUTO_INCREMENT PRIMARY KEY,
    pizza_id INT,
    cust_id INT,
    order_date TIMESTAMP,
    order_quantity INT,
    order_notes VARCHAR (255),
    FOREIGN KEY (pizza_id) REFERENCES PIZZA(pizza_id),
    FOREIGN KEY (cust_id) REFERENCES CUSTOMER(cust_id)
);

我的问题是，如果PIZZA_ORDER表中的记录让我们说两个不同的披萨，意味着两个不同的pizza_ids，它将如何运作？我只是想让PIZZA_ORDER的主键不唯一，每个实际订单都有x个记录。但我不确定这是怎么回事。再次感谢你们对此有所了解。

Answer 1

销售订单包含多个销售订单行项目

create table orders (
  id int primary key,
  ...
);

create table order_items (
  order_id int references orders(id),
  line int,
  pizza_id int references pizza(id),
  ...
  primary key (order_id, line)
);

请参阅https://dba.stackexchange.com/questions/12991/ready-to-use-database-models-example/23831#23831以节省时间：）

Answer 2

您应该在pizza_order到pizza表之间以及Customer到pizza_order表之间建立关系。这就像说，每个披萨都与一个/多个披萨订单有关;而每个披萨订单都与一个/多个客户有关。

CREATE TABLE PIZZA_ORDER
(
    pizza_order_id INT AUTO_INCREMENT PRIMARY KEY,
    order_date TIMESTAMP,
    order_quantity INT,
    order_notes VARCHAR (255),
    cust_id int,
    FOREIGN KEY (cust_id) REFERENCES CUSTOMER(cust_id)
);

CREATE TABLE PIZZA
(
    pizza_id INT AUTO_INCREMENT PRIMARY KEY,
    pizza_name VARCHAR (255),
    pizza_desc VARCHAR (255),
    pizza_price DOUBLE,
    pizza_order_id INT,
    FOREIGN KEY (pizza_order_id) REFERENCES PIZZA_Order(pizza_order_id)
);

外键关系没有意义，有更好的方法吗？

2 个答案: