Question

Hey I am using the following tables. My table course_enrollments references the user_id and the course_id. Both columns combined are set unique.

users
course_enrollments
courses

Rails sets primary keys by default. I have read some articles of people who used these kind of join tables without any pk. e.g. by defining :id => false

Is it appropriate for this kind of join table? what about people enrolling or leaving courses or the search for enrollments. Thanks for your time!

Answer 1

You generally see :id => false on the migration for your join table when you want to use has_and_belongs_to_many, since Rails really doesn’t like finding an :id primary key on these.

From the has_and_belongs_to_many docs

The join table should not have a
primary key or a model associated with
it.