为什么在迁移没有时间戳时会创建created_at / updated_at？

Question

我使用rails 3.2进行以下迁移，并且created_at / updated_at都生成了。我的印象是添加t.timestamps是导致这些列生成的原因。

class CreateContactsCountries < ActiveRecord::Migration
  def change
    create_table :contacts_countries do |t|
      t.string :name, :official_name, :null => false
      t.string :alpha_2_code, :null => false, :limit => 2
      t.string :alpha_3_code, :null => false, :limit => 3
    end

    add_index :contacts_countries, :alpha_2_code
  end
end

Answer 1

请删除该表并再次检查

By default, the generated migration will include t.timestamps (which creates 
the updated_at and created_at columns that are automatically populated 
by Active Record).

参考this