How to use Eloquent model property in subquery? - php

Question

I have two tables (users, posts) and I'm trying to order users according to recent post's date.
But unfortunately I couldn't find a way to use User model's firebase_id to use in subquery. I don't want to use raw query or DB directly if it's possible to use Eloquent for such query.
How can I use User model's firebase_id as subquery parameter?
Here is my non-working code to give an idea about what I try to do:
User::select('users.*', DB::raw("SELECT MAX(id) FROM posts WHERE posts.firebase_id = users.firebase_id as recent_post_date"))
->whereHas('posts', function ($q) {
$q->withCount('comments');
})
->with(['posts' => function ($q) {
$q->withCount('comments')
->orderBy('created_at', 'ASC');
}])
->orderBy('recent_post_date', 'DESC')
->get();

Answer 1

You can use selectSub to add a subquery.
Try the following
$recentPostQuery = Post::select('created_at')
->whereColumn('firebase_id', 'users.firebase_id')
->latest()
->limit(1)
->getQuery();
User::select('users.*')
->selectSub($recentPostQuery, 'recent_post_date')
->whereHas('posts', function ($q) {
$q->withCount('comments');
})
->with(['posts' => function ($q) {
$q->withCount('comments')
->orderBy('created_at', 'ASC');
}])
->orderBy('recent_post_date', 'DESC')
->get();

Answer 2

You can do with QueryBuilder and a join:
$users = DB::table('users')
->join('posts.firebase_id ', '=', 'users.firebase_id ')
->orderBy('posts.recent_post_date', 'DESC')
->get();
UPDATE
You asked for Eloquent. You can do it with whereHas.
$users = User::whereHas('posts', function (Builder $query) {
$query->orderBy('posts.recent_post_date', 'DESC');
})->get();