Should there be a separate table when mapping one to many relationship?

Question

In terms of performance and scalability which one would be a better method to do one to many mappings in MySQL.

• Using a separate column but sticking to 2 tables:

  (person) : id, name

  (phone) : id, number, type, person_id

• Using a separate table:

  (person) : id, name

  (phone) : id, number, type

  (person_phone) : id, person_id, phone_id

Answer 1

There's only one correct answer to this, and it's the first one.

The second of your ideas is how you model many-to-many relationships, not one-to-many.

Answer 2

In terms of performance it is always cheaper to avoid joins, which add multiplicity to the amount of rows to be queried.

As long as a single phone will only be used by one employee (a true one-to-many) the first option is best.