如何引用另一个表中的多行？ [英] How can you reference multiple rows in another table?

问题描述

假设我有一张角色表，例如，

Let's suppose I have a table of roles, for example,

Roles
-----
ID  Name
0   Salesman
1   Client
2   Manager

让我们还假设这些角色不是互斥的：也就是说，一个人可以同时担任推销员，客户和经理。

Let's also suppose that these roles are not mutually exclusive: that is, a person can be a salesman, a client, and a manager all at the same time.

如果我有一个具有角色字段的 Person 表，我如何能够引用<$ c中的多行$ c> Roles 表？

If I have a Person table with a Role field, how am I able to reference multiple rows in the Roles table?

推荐答案

您引入了一个引用了两个原始表的新表：

You introduce a new table that references both of the original tables:

CREATE TABLE PersonRoles (
    PersonID int not null,
    RoleID int not null,
    constraint PK_PersonRoles PRIMARY KEY (PersonID,RoleID),
    constraint FK_PersonRoles_Persons FOREIGN KEY (PersonID) references Person (ID),
    constraint FK_PersonRoles_Roles FOREIGN KEY (RoleID) references Role (ID)
)

假设多重度为 m：n ，则以上是正确的。我做出的假设（未在您的问题中列出）是一个以上的人可以推销员。

Assuming that the multiplicity is m:n, the above is correct. I made the assumption (not listed in your question) that more than one person can be e.g. a Salesman.

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