Multiple connections in Codeigniter (active records)

I am trying to get results from my database with details covering the tables "places", "category" and "reviews", and then sort by the number of reviews. When I add the second connection, only one row is retrieved.

$this->db->select('places.*, category.*')
            ->from('places')
            ->join('category', 'places.category_id = category.category_id')
            ->join('places_reviews', 'places_reviews.place_id = places.id')
            ->where('places.category_id', $category_id)
            ->limit($limit, $offset)
            ->order_by($sort_by, $sort_order);

I did not add IFNULL(COUNT(places_reviews('review_id')) AS 'num_reviews', 0)select () to the code to clear the code.

Any ideas?