gistfile1.rb

order = Order.new(:company => company)
order.events >>
Wed, 04 Feb 2009 12:29:46 GMT ~ debug ~ (0.000211) SELECT `id`, `type`, `order_id`, `details`, `body` FROM `events` WHERE `order_id` IS NULL ORDER BY `id`

gistfile2.rb

>> order = Order.create
=> #<Order id=107912 ... >
>> event = order.events.new(:type => OrderEvent)
=> #<Event id=nil type=OrderEvent order_id=107912 ...>
>> event.order_id
=> 107912
>> event.save
=> true
>> event.order_id
=> 107912
>> event.reload
=> #<Event id=32 type=OrderEvent at=#<DateTime: 53025127771/21600,1/24,2299161> order_id=nil ...>
>> event.order_id
=> nil

SQL:
~ debug ~ (0.000071) SET SESSION sql_mode = 'ANSI,NO_AUTO_VALUE_ON_ZERO,NO_DIR_IN_CREATE,NO_ENGINE_SUBSTITUTION,NO_UNSIGNED_SUBTRACTION,TRADITIONAL'
~ debug ~ (0.001257) INSERT INTO `orders` (`created_at`) VALUES ('2009-02-04 13:37:41')
~ debug ~ (0.062815) INSERT INTO `events` (`type`, `at`) VALUES ('OrderEvent', '2009-02-04 13:38:04')
~ debug ~ (0.047902) SELECT `id`, `type`, `at`, `title`, `order_id`, ... FROM `events` WHERE `id` = 32