Where should I store a foreign key?

Question

If I have a relationship between two tables (both tables have their own primary keys) what should guide my decision as to which table should store the foreign key? I understand

Answer 1

"What is a systematic way of making that decision though?"

There appear to be two choices: The "One" side as FK's to the "Many side", or the "Many" Side has FK's to the "One" side.

Let's actually look a the choices.

• All the rows of the "Many" side can easily reference one row on the "One" side.

• The one row on the "One" side cannot ever reference ALL of the rows on the "Many" side.

Only one technique works: "Many" side has FK to "One" side.

There is only one actual implementation choice. There's no "decision".