Need help related to my codeigniter wallpaper script

Hi, can you run this? And post the generated SQL. Can't really see where the category are.
It would also be helpful with a database structure, not the data. But what the tables/columns are named.

PHP Code:

public function get_parent_categories()
    {
        $views = $this->wallpaperViews();
        $this->db->select('wp.category_seq_id as wpcid,w.*');
        $this->db->from('wallpapers_path wp');
        $this->db->join('wallpapers w', 'w.wallpaper_seq_id = wp.wallpaper_seq_id');
        $this->db->join("($views) as v", 'v.wv_wid = w.wallpaper_seq_id', 'left');
        $this->db->group_by('wp.category_seq_id');
        $this->db->order_by('total_views', 'desc');
        echo $wallpaper_sql = $this->sql();

        $this->db->select('w.*');
        $this->wallCatTemplate(false);
        $this->db->join("($wallpaper_sql) as w", 'w.wpcid = c.category_seq_id', 'left');
        $this->db->where('w.wallpaper_seq_id IS NOT NULL');
        $this->db->order_by('t2.category_name', 'asc');
        echo $this->sql();
    }