For everyone normalizing their designs, just remember: There ain't no such thing as a partial foreign key. When a project pretends that partial foreign keys are a valid concept, the end result is a ...

To link databases together to create a relational database, a foreign key is used. A foreign key is a field in one table that is linked to the primary key in another table.

Retaining an infinitude of Foreign Keys may cause future performance bottlenecks as transactional volume will get a performance hit by maintaining all those foreign keys and the indexes behind them.