How to get average with orderBy Desc in Laravel 5 - php

Question

I have 2 tables in my database.
books and ratings
in books
id, name
in ratings
id, book_id, rating
i have set has many relationship for these models.
So in Book model -
public function ratings()
{
return $this->hasMany('App\Rating');
}
in Rating Model -
public function book()
{
return $this->belongsTo('App\Book');
}
Now i want to fetch all books with there average rating but order by high rating.
so i high rated books first and then low ratings.
So How i can join 2 tables to achieve this result.
Thanks.

Answer 1

You can use a modified withCount():
$books = Book::withCount(['ratings as average_rating' => function($query) {
$query->select(DB::raw('coalesce(avg(rating),0)'));
}])->orderByDesc('average_rating')->get();

Answer 2

Books::withAvg('ratings', 'rating')->orderBy('ratings_avg_rating', 'desc')->take(5)->get();
this works in Laravel 8

Answer 3

Via Collections*
$books = Book::with('ratings')
->get()
->sortBy(function($bk, $key) {
if($bk->rating) {
return $bk->rating->rating;
}
return null;
});
Via Joins
$books = Book::join('rating', 'rating.book_id', '=', 'book.id')
->orderBy('ratings.rating', 'desc')
->select('books.*')
->get();

Answer 4

That query would look something like this:
SELECT book.id, AVG(ratings.rating) AS avg_rating
FROM ratings
JOIN book ON book.id = ratings.book_id
/* WHERE AVG(ratings.rating) > 4 You could say only return results where rating > 4 */
GROUP BY book.id
ORDER BY AVG(ratings.rating) DESC LIMIT 5;
You need to join the two tables, use an aggregate function with a group by on the book. Then just sort and limit the results.
UPDATE:
In response to your question:
SELECT book.id, COALESCE(AVG(ratings.rating), 0) AS avg_rating
FROM book
*LEFT* JOIN ratings ON book.id = ratings.book_id
GROUP BY book.id
ORDER BY AVG(ratings.rating);
Use of a view might be something of a compromise between ease of the ORM and sanity in your querying.