外键可以成为另一个表的组合主键的一部分吗? [英] Can a Foreign Key be part of a Composite Primary Key for another table?

问题描述

我在音乐数据库中有两个(很多)表:

I have two(of many) tables in a music database:

音乐会:ArtistID，ConcertID，ConcetName，VenueID ConcertDetails:ConcertDate，ConcertID，费用

Concerts: ArtistID,ConcertID,ConcetName,VenueID ConcertDetails: ConcertDate, ConcertID, Cost

如您所见，ConcertDetails表使用了ConcertID表中的ConcertID.我将ConcertDate& amp; ConcertID为ConcertDetails制作一个复合主键.但是，由于这与Concerts表中的ConcertID有关，因此它也必须是外键.这样可以吗?

The ConcertDetails tables as you see, uses ConcertID which is also in the Concerts table. I combine ConcertDate & ConcertID to make a Composite Primary Key for ConcertDetails. However since this relates to ConcertID from Concerts table it also needs to be a Foreign Key. Is this ok to do?

推荐答案

当然可以.主键的子集通常是外键.例如，任何多对多表都可以执行此操作.就您而言:

Yes, of course. It's common for a subset of a primary key to be a foreign key. Any many-to-many table does this for instance. In your case:

CREATE TABLE ConcertDetails (
  ConcertDate DATE NOT NULL,
  ConcertID INT NOT NULL,
  PRIMARY KEY (ConcertDate, ConcertID),
  FOREIGN KEY (ConcertID) REFERENCES Concerts(ConcertID)
);

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