```ruby
class AddPhysicalIdToServerspecSchedule < ActiveRecord::Migration
  def change
    add_column :serverspec_schedules, :physical_id, :string, null: false
  end
end
```

Change a NOT NULL column to allow NULL
user
```ruby
class AddPhysicalIdToServerspecSchedule < ActiveRecord::Migration
  def change
    add_column :serverspec_schedules, :physical_id, :string
  end
end
```
assistant