mysql中的复合外键是什么? [英] What is a composite foreign key in mysql?

问题描述

在我使用的框架 (yii) 的文档中看到这个术语(复合外键).什么是复合外键(在 mySql 数据库中)?

Seeing this term (composite foreign key) in the documentation for a framework I am using (yii). What is a composite foreign key (in a mySql database)?

(我的猜测是，给定两个表之间的关系，一个表有一个与另一个表的 id 同名的列.)

*免责声明:我做了尽职调查，在谷歌上搜索了整整两分钟，但没有找到该术语的最终定义.

*Disclaimer: I did my due diligence and Googled this for like two whole minutes but found no conclusive definition for the term..

推荐答案

composite key 由多个属性来唯一标识一个实体强>发生.这与复合键的不同之处在于，组成键的一个或多个属性本身并不是简单的键.

A composite key consists of more than one attribute to uniquely identify an entity occurrence. This differs from a compound key in that one or more of the attributes, which make up the key, are not simple keys in their own right.

例如，您有一个保存 CD 收藏的数据库.其中一个实体称为轨道，它保存 CD 上轨道的详细信息.这有一个组合键，由 CD 名称、曲目编号组成.

For example, you have a database holding your CD collection. One of the entities is called tracks, which holds details of the tracks on a CD. This has a composite key of CD name, track number.

曲目实体中的CD名称是一个简单的键，链接到CD实体，但曲目编号本身并不是一个简单的键.

CD name in the track entity is a simple key, linking to the CD entity, but track number is not a simple key in its own right.

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