if coulmn of mysql is empty you get value from other table with same name of coulmn in codeigniter
Assuming the column name is name
$this->db->select('coalesce(w.name, t.name) as tournament_name, w.tournament_id,<all other tournament_week fields>');
COALESCE function should work.Try following.
$this->db->select('COALESCE(w.name, t.name) tournament_name); $this->db->from('tournament_week w'); $this->db->join('tournament t', 'w.tournament_id = t.id'); $this->db->where('w.tournament_id=', $tid); $this->db->where('w.show_week', 1); $this->db->order_by("w.week_no", "ASC"); $query = $this->db->get()->result_array(); return $query;