mysql - 如何将 UserID 和 ProductID 列作为下载表中的外键？

Question

这就是我到目前为止所做的!!

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创建数据库MyWebDB;

创建表用户

( UserID Int Primary Key,
  EmailAddress Varchar(50) Not Null, 
  FirstName Varchar(50) Not Null, 
  LastName Varchar(50) Not Null)

创建表下载

( DownloadID int Primary Key, 
  DownloadDate SmallDatetime Null, 
  FileNames Varchar(100) Not Null, 
  Foreign Key (UserID) References Users(UserID),
  Foreign Key (ProductID) References Products(ProductID))

创建表产品

(ProductID int primary key, ProductName Varchar(50))

我的SQL查询

Answer 1

您必须为下载表 UserID 和 ProductID 设置数据类型

 Userid int FOREIGN KEY REFERENCES Users(UserID)
 Productid int FOREIGN KEY REFERENCES Products(ProductID)

或

Userid int,
Productid int,
FOREIGN KEY (Userid) REFERENCES Users(UserID),
FOREIGN KEY (Productid) REFERENCES Products(ProductID))

喜欢:

创建表下载

( DownloadID int Primary Key, 
  DownloadDate SmallDatetime Null, 
  FileNames Varchar(100) Not Null, 
  Userid int,
  Productid int,
  FOREIGN KEY (Userid) REFERENCES Users(UserID),
  FOREIGN KEY (Productid) REFERENCES Products(ProductID))