code: public function getUsers() {
          $select = $this->tableGateway->getSql()->select();
          $select->columns(["fullname" => new Expression("DISTINCT(CONCAT(usr_firstname, ' ', usr_lastname))")]);
          $select->join('melis_core_user',
              'melis_core_user.usr_id = melis_hist_page_historic.hist_user_id',
              [],
              $select::JOIN_INNER
          );
          $resultSet = $this->tableGateway->selectWith($select);
  
          return $resultSet;
      }
docs: This will return all users
  @return mixed