**Model Search Method**

```
  $criteria->alias = 'c';
  $criteria->select = 'c.*,max(ca.date) AS lastactivity';
  $criteria->join = 'LEFT JOIN tbl_contact_action AS ca ON (ca.contact_id=c.contact_id)';
  $criteria->condition = 'c.status<>"Deleted"';
  $criteria->group = 'c.contact_id';
  $criteria->order = 'lastactivity DESC';

$sort = new CSort;
        $sort->defaultOrder = array('lastactivity' => CSort::SORT_DESC); //'name ASC';        
        $sort->attributes = array(
            'name' => 'name',
            'email' => 'email',
            'status' => 'status',
            'createdon' => 'createdon',
            'lastactivity' => 'lastactivity',
        );
        $sort->applyOrder($criteria);
        return new CActiveDataProvider($this, array(
            'criteria' => $criteria,
            'sort' => $sort,            
        ));

```

Basically, I have a 1:n relationship where in I need only latest record from child table. The parent table data will be displayed based on the comment that is done latest in child table. How to make this field sortable ?

**Error**

CDbCommand failed to execute the SQL statement: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'c.lastactivity' in 'order clause'.