How to get all Users orderBy their ratings using Laravel 5 / Eloquent / query builder

i have these tables in my database.

users

id username

then

books

id name user_id

ratings

id rating book_id

Now i want to fetch all the users and list them on the webpage but i need them to be order by ratings. So basically i need to check all users and their books then calculate the average rating of those books then get users according that average rating.

How can i do this using laravel or query builder?

i have relationship setup as following

User model

 public function books()
    {
        return $this->hasMany('App\Book');
    }

Book model

 public function ratings()
    {
        return $this->hasMany('App\Rating');
    }

Rating model

 public function book()
    {
        return $this->belongsTo('App\Book');
    }

P.S. if there is no rating for particular book then i want to return 0 ratings instead of null so in my webpage i could display that users rating as 0 Thanks.

via Chebli Mohamed