添加更多uploadFile字段问题

I want to add small image to my slider in CMS. Currently what I have down here works for me, I have one big Image:

class Banner extends SortableObject {

    private static $db = array(
    );

    private static $has_one = array(
        'HomePage' => 'HomePage',
        'Image' => 'Image',
        'Target' => 'Page',
    );

    private static $summary_fields = array(
        'ID',
        'Target.MenuTitle',
    );

    public function getCMSFields() {
        $fields = new FieldList();

        $img = new UploadField('Image');
        $img->setFolderName('hpbanners');
        $img->getValidator()->setAllowedExtensions(array('jpg','gif','png'));
        $fields->push($img);

        $drop = new TreeDropdownField('TargetID','Choose page','SiteTree');
        $fields->push($drop);

        return $fields;
    }
}

Now I want to add another field. I added $smallImage, as I understand this should add new column in DB, just like Image before, but my problem is that in DB table I have only first image, second is not added:

class Banner extends SortableObject {

    private static $db = array(
    );

    private static $has_one = array(
        'HomePage' => 'HomePage',
        'Image' => 'Image',
        'SmallImage' => 'SmallImage',
        'Target' => 'Page',
    );

    private static $summary_fields = array(
        'ID',
        'Target.MenuTitle',
    );

    public function getCMSFields() {
        $fields = new FieldList();

        $img = new UploadField('Image');

        $img->setFolderName('hpbanners');
        $img->getValidator()->setAllowedExtensions(array('jpg','gif','png'));
        $fields->push($img);

        $smallImage = new UploadField('SmallImage');
        $smallImage->getValidator()->setAllowedExtensions(array('jpg','gif','png'));
        $fields->push($smallImage);

        $drop = new TreeDropdownField('TargetID','Choose page','SiteTree');
        $fields->push($drop);

        return $fields;
    }
}

So please tell me, as I know this column will be automatically added, should I clear cache or what am I doing wrong? Help me! :)

Relations are always in form of 'YourRelationName' => 'Type'. So your $has_one relation definition should read:

private static $has_one = array(
    'HomePage' => 'HomePage',
    'Image' => 'Image',
    'SmallImage' => 'Image', // Use type 'Image', not 'SmallImage'
    'Target' => 'Page',
);