Activedropdown On Change Event

this is my view:

<?php
$em=EmployerJobs::model()->findAll();
$model = new EmployerJobs();
$list = CHtml::listData($em,'Employer_JobsJobCode','Employer_JobsJobCode');
echo CHtml::activeDropDownList($model,'Employer_JobsJobCode',$list, array('empty' => 'Please Select'));
?>

it's working fine, select making a list of values from table called employerjobs,

now i need to create onchange event for dropdown, if i change value in dropdown it should retrive particular row details.

im newbie on yii, i confused, i seeking for help. TIA