ruby数据库表添加字段、修改字段类型、修改字段名称

class AddColumnToDGroupsEquipNum < ActiveRecord::Migration[5.1]
　　def change
　　　　add_column :d_groups, :equip_num ,:integer
　　end
end

class ChangeColumnToDGroupsEquipNum < ActiveRecord::Migration[5.1]
   def change
      change_column :d_groups, :equip_num, :string
   end
end

class ChangeColumnToDGroupsEquipNumEquipNums < ActiveRecord::Migration[5.1]
  def change
    rename_column :d_groups, :equip_num, :equip_nums
  end
end