How to properly build a YII query?

Question

Yii

There is a simple request

$criteria = new CDbCriteria();
$criteria->group = 't.project_id';
return $this->findAll($criteria);

but I also need to calculate the average of one field in this query

$criteria->select = new CDbExpression('*, AVG(optimisation)');

I tried this, it doesn't work,
in fact, you need to execute this query
SELECT *, AVG(`optimization`) FROM `table` ORDER BY `project_id`

Answer 1

Maybe so?
$criteria->select = array( '*', new CDbExpression('AVG(optimisation)') );