Leaderboard Query

public function findLeadersBySchool($schoolId = 1, $limit = 3)
	{
	      return $this->findLeadersBaseQuery()
     	                ->leftJoin('u.Assignment_Assignee a ON u.id = a.assigned_entity_id ')
                     	->addWhere('a.assigned_entity_type = ?', User_Model_Student::ENTITY_TYPE)
             		    ->addWhere('a.assignee_entity_type = ?', Plan_Model_Classroom::ENTITY_TYPE)
             		    ->addWhere('a.assignee_entity_id = ?', $schoolId)
             		    //->limit($limit)
         	            ->execute();
	}
	
    public function findLeadersBaseQuery()
    {
        return $this->getTable()
	                ->createQuery()
	                ->select("SUM(c2.steps_per_minute * c.minutes) AS steps, u.username as username")
	                ->from("Challenge_Model_ActivityLog c")
	                ->leftJoin("c.Challenge_Activity c2")
	                ->leftJoin("c.Challenge_Profile c3")
	                ->leftJoin("c3.User_Student u");
    }