主键和外键 [英] Primary and Foreign Key at the same time

问题描述

在SQL Server 2008中有可能创建一个由两列同时创建主键和外键的表？如果是，那么这样的代码将如何？我搜索了一下，结果什么也没有。

Would it be possible in SQL Server 2008 to have a table created with 2 columns that are at the same time primary and foreign keys? If yes, how would such a code look like? I've searched and came up with nothing.

推荐答案

当然，没问题：

Sure, no problem:

CREATE TABLE dbo.[User]
(
  Id int NOT NULL IDENTITY PRIMARY KEY,
  Name nvarchar(1024) NOT NULL
);

CREATE TABLE [Group] 
(
  Id int NOT NULL IDENTITY PRIMARY KEY,
  Name nvarchar(1024) NOT NULL
);

CREATE TABLE [UserToGroup]
(
  UserId int NOT NULL,
  GroupId int NOT NULL,
  PRIMARY KEY CLUSTERED ( UserId, GroupId ),
  FOREIGN KEY ( UserId ) REFERENCES [User] ( Id ) ON UPDATE  NO ACTION  ON DELETE  CASCADE,
  FOREIGN KEY ( GroupId ) REFERENCES [Group] ( Id ) ON UPDATE  NO ACTION  ON DELETE  CASCADE
);

这是模拟多对多关系的常用方法。

This is quite commonly used to model many-to-many relations.

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