Question

如果我在SQL Server 2008中使用以下SQL命令来更新具有外键约束的表：

ALTER TABLE Employees
ADD FOREIGN KEY (UserID)
REFERENCES ActiveDirectories(id)

UserID 是Employees表中的FK列。我正在尝试在UserID表格中引用 ActiveDirectories 。我收到此错误：

外键'UserID'在引用时引用了无效的列'UserID' 表'员工'。

Answer 1

错误表示Employees表中没有UserID列。首先尝试添加列，然后重新运行该语句。

ALTER TABLE Employees
ADD CONSTRAINT FK_ActiveDirectories_UserID FOREIGN KEY (UserID)
    REFERENCES ActiveDirectories(id);

Answer 2

也许你倒退了你的专栏？

ALTER TABLE Employees
ADD FOREIGN KEY (UserID)           <-- this needs to be a column of the Employees table
REFERENCES ActiveDirectories(id)   <-- this needs to be a column of the ActiveDirectories table

可能是ID表中的列Employees和UserID表中的ActiveDirectories？

然后你的命令应该是：

ALTER TABLE Employees
ADD FOREIGN KEY (ID)                   <-- column in table "Employees"
REFERENCES ActiveDirectories(UserID)   <-- column in table "ActiveDirectories"

Answer 3

MySQL / SQL Server / Oracle / MS Access：

ALTER TABLE Orders
ADD FOREIGN KEY (P_Id)
REFERENCES Persons(P_Id)

要允许命名FOREIGN KEY约束，并在多列上定义FOREIGN KEY约束，请使用以下SQL语法：

MySQL / SQL Server / Oracle / MS Access：

ALTER TABLE Orders
ADD CONSTRAINT fk_PerOrders
FOREIGN KEY (P_Id)
REFERENCES Persons(P_Id)

Answer 4

如果已创建表：

首先要做：

ALTER TABLE `table1_name` ADD UNIQUE( `column_name`);

然后：

ALTER TABLE `table1_name` ADD FOREIGN KEY (`column_name`) REFERENCES `table2_name`(`column_name`);

Answer 5

外键创建的方式对于ActiveDirectories（id）是正确的，我认为主要的错误是你没有在ActiveDirectories表中提到id的主键

Answer 6

ALTER TABLE Faculty 
WITH CHECK ADD  CONSTRAINT FKFacultyBook
FOREIGN KEY FacId
REFERENCES Book Book_Id

ALTER TABLE Faculty 
WITH CHECK ADD  CONSTRAINT FKFacultyStudent 
FOREIGN KEY FacId
REFERENCES Student StuId

Answer 7

将来。

ALTER TABLE Employees
ADD UserID int;

ALTER TABLE Employees
ADD CONSTRAINT FK_ActiveDirectories_UserID FOREIGN KEY (UserID)
    REFERENCES ActiveDirectories(id);

SQL将外键添加到现有列

7 个答案: