Optimize db query

Hi everybody,
everything is working fine with my code but i'm willing to know if there is a way to optimize, queries, db connections etc
when it's needed a lot different data from different tables.. somehing like UNIONS or JOINS don't seem to be the case to me but maybe they have other meaning too..
p.s. I know the code should be organized in model functions, this is just an example..
Thanks a lot for your suggestion!

PHP Code:

public function index($service_id)
{

  $data['service'] = $this->db->table('services')
                              ->select('*')
                              ->getWhere(['id' => $service_id],1)
                              ->getRowArray();

  $data['doctors'] = $this->db->table('doctors')
                              ->select('id,name,surname')
                              ->get()->getResult();

  $data['specialty'] = $this->db->table('specialties')
                                ->select('*')
                                ->getWhere(['id' => $data['service']['specialty_id']],1)
                                ->getRowArray();

  $data['studios'] = $this->db->table('studios')
                              ->select('id,city,address')
                              ->get()->getResult();

  $data["main_content"] = "pages/service_view";
  return view("layouts/main_layout",$data);
}