redmine/db/migrate/20090406161854_add_parent_id_to_enumerations.rb

class AddParentIdToEnumerations < ActiveRecord::Migration[4.2]
  def self.up
    add_column :enumerations, :parent_id, :integer, :null => true, :default => nil
  end

  def self.down
    remove_column :enumerations, :parent_id
  end
end