Question

我运行以下查询以在MS SQL Server中创建表：

CREATE TABLE menus
(
  menu_id int NOT NULL PRIMARY KEY,
  menu_name char,
  other_details char
)

CREATE TABLE bookings
(
  booking_Id int NOT NULL PRIMARY KEY,
  date_booked DATE,
  date_of_booking DATE,
  other_details char,
  staff_id int FOREIGN KEY REFERENCES staff(staff_id),
  customer_id int FOREIGN KEY REFERENCES customers(customer_id)
)

CREATE TABLE menus_booked
(
  menu_id INT NOT NULL,
  booking_id INT NOT NULL,
  CONSTRAINT PK_menus_booked PRIMARY KEY(menu_id,booking_id),
  FOREIGN KEY (menu_id) REFERENCES menus(menu_id),
  FOREIGN KEY (booking_id) REFERENCES bookings(booking_id)
)

CREATE TABLE menu_changes
(
  change_id int NOT NULL PRIMARY KEY,
  menu_id int NOT NULL,
  booking_id int NOT NULL,
  change_details char,
  FOREIGN KEY (menu_id) REFERENCES menus_booked(menu_id),
  FOREIGN KEY (booking_id) REFERENCES menus_booked(booking_id)
)

在运行最后一个查询时，我收到错误：

参考表中没有主键或候选键＆quot; menus_booked＆＃39;与外键中的引用列列表匹配＆＃39; FK_menu_chan_menu＆＃39;

我不确定我的查询是否正确，无法解决此错误。

Answer 1

menus_booked的主键是menu_id和booking_id的唯一组合。外国人必须指出这种组合，而不仅仅是其中一个领域，这不一定是唯一的。您的查询当前尝试定义两个外键，每列一个，而不是列的组合上的一个外键：

CREATE TABLE menu_changes
(
    change_id int NOT NULL PRIMARY KEY,
    menu_id int NOT NULL,
    booking_id int NOT NULL,
    change_details char,
    FOREIGN KEY (menu_id, booking_id) 
        REFERENCES menus_booked(menu_id, booking_id) -- Here!
)

Answer 2

外键必须引用primary key（或unique key，但此处PK是问题），并且必须完整引用它。

FOREIGN KEY (menu_id) REFERENCES menus_booked(menu_id),
FOREIGN KEY (booking_id) REFERENCES menus_booked(booking_id)

您有两个外键引用了menus_booked主键的一部分。您必须将其更改为：

FOREIGN KEY (menu_id, booking_id) REFERENCES menus_booked(menu_id, booking_id)

在SQL Server中设置外键时出错

2 个答案: