Ruby on Rails-Datenbankmigration erstellt keine Fremdschlüssel in MySQL-Tabellen

Sie können den Foreigner verwenden gem.

Ändern Sie dann Ihre Migration wie folgt:

class CreateBookCheckOuts < ActiveRecord::Migration
  def self.up
    create_table :book_check_outs do |t|
      t.integer :book_id, :null => false
      t.integer :person_id, :null => false
      t.datetime :OutDate, :null => false
      t.datetime :ReturnDate, :null => true

      t.timestamps
    end
    add_foreign_key(:book_check_outs, :books)
    add_foreign_key(:book_check_outs, :people)
  end

  def self.down
    remove_foreign_key(:book_check_outs, :books)
    remove_foreign_key(:book_check_outs, :people)
    drop_table :book_check_outs
  end
end