13. Foreign Key
A foreign key is used to link tables together and create a relationship. It is a field in one table that is linked to the primary key in another table.
In the database above there are three tables:
The primary key in the Artists table is: ArtistID
The primary key in the Genre table is: GenreID
These primary keys link to identically named fields in the Recordings table. Each of those identically named fields are known as a 'foreign key'
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Click on this link: Foreign Key