drop down list in yii

i want to add dependent dropdown list in my form so please somebody tell me how to fill that data here is my code.& please explain me in detail actually i am newbie in yii framework.

my problem is that i m not getting data from database n my database name is ‘countries’ & i want to show these countries in my form

<div class="row">

    &lt;?php echo &#036;form-&gt;labelEx(&#036;model,'Country'); ?&gt;

    &lt;?php echo &#036;form-&gt;dropDownList(&#036;model,'Country',CHtml::listData(Country::model()-&gt;findAll(), 'country_id', 'country_name'));?&gt;

    &lt;?php echo &#036;form-&gt;error(&#036;model,'Country'); ?&gt;


help yourself http://www.yiiframework.com/wiki/24/