通过关系命令分页（Laravel 5.3）

Question

In my app I have posts. I wish to show all the posts on the homepage, but order them higher if the post's user has uploaded an image. I can determine if the post's user has uploaded an image by checking if the user has a relationship with a row in the images table, like this:

$post->user->image 

My code currently looks like this:

$posts = Post::where('subject_id', '=', $subject->id)
        ->approved()
        ->orderBy('created_at', 'desc')
        ->paginate(18);

Currently, I am simply ordering it by created at, but ideally all posts whose related user has an image will come first, then the rest. I've been looking for a way to do this efficiently and in a way that doesn't just work on the first page.

How should I go about this?

Answer 1

Try this:

$posts = Post::where('subject_id', '=', $subject->id)
        ->approved()
        ->select(['*', DB::raw('(SELECT count(images.id) FROM images INNER JOIN users ON users.image_id = images.id WHERE posts.user_id = users.id) as count_images'])
        ->orderBy('count_images', 'desc')
        ->orderBy('created_at', 'desc')
        ->paginate(18);

Answer 2

Try this:

$posts = Post::where('subject_id', '=', $subject->id)
         ->approved()
         ->with('user')
         ->join('users', 'users.id', '=', 'post.user_id')
         ->select(['post.*', 'users.avatar'])
         ->orderBy('image', 'desc')
         ->orderBy('created_at', 'desc') // ->latest() can be used for readability
         ->paginate(18);

This code eager loads users to reduce number of DB queries and doesn't use raw queries which should be avoided, because mistake can make your application vulnerable to SQL injection.

Explanation:

We eager load relationship using ->with('user') method, then join users table, select all fields from posts table and only image field from users table, then order results by image and paginate results.

Result should look like this:

App\\Post:

• id
• title
• ...
• image(from users table)
• App\\User (eager loaded relationship)
  • id
  • name
  • email
  • ...
  • image
  • created_at