Run this command to generate the empty migration file (it is not automatically populated, you need to populate it yourself):
rails generate migration assignments_security_users
Open up the generated migration file and add this code:
class AssignmentsSecurityUsers < ActiveRecord::Migration
def change
create_table :assignments_security_users, :id => false do |t|
t.integer :assignment_id
t.integer :security_user_id
end
end
end
Then run rake db:migrate
from your terminal. I created a quiz on many_to_many relationships with a simple example that might help you.