外键约束 [英] foreign key constraint

问题描述

我们可以在一个表中有一个或多个外键.

can we have one or more foreign key in one table.

推荐答案

是的！但是每个外键约束都将进入其自己的字段.联接表是表的一个很好的例子，在大多数情况下，表仅具有外键.这是在关系数据库中创建的多对多关系.

祝你好运！

Yes you can! But each foreign key constraint would go in its own field. A join-table is a good example of a table that, in most cases, only has foreign keys. This is how many-to-many relations are created (in relational database ).

Good luck!

是的.

请参见以下示例:

http://www.w3schools.com/sql/sql_foreignkey.asp [

yes.

see the following for examples:

http://www.w3schools.com/sql/sql_foreignkey.asp[^]

create table A
(
id int constraint PK_D primary key,
idb int constraint FK_D_IDB foreign key references B(id),
idc int constraint FK_D_IDC foreign key references C(id),
);

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