mysql error with query builder

Yii 1.1 General Discussion
1

I’m trying to build a custom sql query with query builder. However, I’ve got a problem with it.




$sql = "SELECT m.* FROM tbl_messages m LEFT JOIN tbl_bids b ON (m.message_id = b.message_id) WHERE m.project_id=:project_id AND b.bid_id is null";

        $command = Yii::app()->db->createCommand($sql);

        $command->bindParam(':project_id',$project_id,  PDO::PARAM_INT);

        $messages = $command->queryAll();

-> work




$sql = "SELECT m.* FROM {{messages}} m LEFT JOIN {{bids}} b ON (m.message_id = b.message_id) WHERE m.project_id=:project_id AND b.bid_id is null";

-> generate 1064 error




        $sql = "SELECT m.* FROM `{{messages}}` m LEFT JOIN `{{bids}}` b ON (m.message_id = b.message_id) WHERE m.project_id=:project_id AND b.bid_id is null";

-> error: Base table or view not found: 1146 Table {{messages}} doesn’t exist.

Can anyone please explain to me why this is happening?