$query = $this->db->query("
                                          SELECT ft_login,fi_system,ft_password,fk_id
                                          FROM users u
                                          INNER JOIN taccountscontent t ON u.id = t.fk_id
                                          WHERE u.id IN (select id from users where id=123)
                                          ");
 $tb = $query->row_array();

 if ( $tb = $query->num_rows() > 0){
         while($row = $query->fetch_array())
             {        
                 echo $row['ft_login'];
              
                }
}