Rails: Join model table migration template

When creating a database table for a join model, you can use this template. For models Student and School:

Copyclass CreateStudentSchools < ActiveRecord::Migration[7.2]
  def change
    create_table :student_schools do |t|
      t.timestamps

      t.references :student, null: false, foreign_key: true
      t.references :school, null: false, foreign_key: true
      
      t.index [:student_id, :school_id], unique: true
    end
  end
end

It sets a few database constraints that ensure data integrity:

• null: false: Prevent join records without associations.
• foreign_key: true: Prevent deleting a joined record. Set dependent: :destroy on your has_many :student_schools association in both models to remove join records together with the model records.
• Index: Prevent duplicate join records.