query binding ของ codeigniter ในกรณีที่ไม่มีค่าใดๆส่งมาในตัวแปร จะเกิดอะไรขึ้น?

if(!empty($id)){
  $this->db->where('member_id',$id);
}
$result = $this->db->get->('job ')->result_array();

print_r($result);

if(!empty($id)){
	$sql = "SELECT jb.job_id,jb.jb_name FROM job as jb WHERE jb.member_id = ?";
	$r = $this->db->query($sql, array($id))->result_array();	
}else{
	$sql = "SELECT jb.job_id,jb.jb_name FROM job as jb";
	$r = $this->db->query($sql)->result_array();	
}

return $r;

        if(! empty($id)):
            $sql = "
                SELECT
                    jb.job_id,jb.jb_name
                FROM
                    job as jb
                WHERE
                    sc.member_id = ?
                GROUP BY
                    jb.jb_name
                ";
             $r = $this->db->query($sql, array($id));
        else:
            $sql = "
                SELECT
                    jb.job_id,jb.jb_name
                FROM
                    job as jb
                GROUP BY
                    jb.jb_name
                ";
              $r = $this->db->query($sql);
        endif;
        return $r->result_array();

$this->db->select('job_id,jb_name');
if(!empty($id)){
  $this->db->where('member_id',$id);
}
$result  = $this->db->group_by('jb_name')
               ->get->('job')
               ->result_array();

print_r($result);