A foreign key is a copy of the primary key. If placed in another table, the two tables then have a link with each other.
Instead, tables use an extra attribute called the foreign key to link tables together.
The foreign key is always placed in the entity that is the "many" entity of the one to many relationship
The reason for this is very simple, each table's cell can only contain one value, it would not make sense to place the playerID foreign key on the team's table
A field in a table that appears as match of the primary key in another table.
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