按最新（最新）相关型号排序 [Laravel]

Question

我正在使用 Laravel 5.4 并且我有以下关系：

论坛 hasMany 主题 (threads())
线程 hasMany Post (posts())
线程 belongsTo 用户 (user())
Post belongsTo 用户 (user())

目前，在我的 ThreadsController@index 中，我有以下内容：

public function index()
{
    $threads = $this->forum->threads()
        ->approved()
        ->withCount(['posts AS approved_replies' => function ($query) {
            $query->where('posts.approved', true)->where('posts.is_starting_thread', false);
        }])
        ->with(['posts' => function ($query) { // Posts
            $query->approved()
                ->with('user') // Author of post
                ->latest();
            }]
        )
        ->with('user') // Author of thread
        ->latest()
        ->paginate(20); 

    return view('forums.threads.index')->with([
        'forum' => $this->forum, 'threads' => $threads
    ]);
}

我的 index.blade.php 应该显示 threads 的列表，其中每个 thread 将有：

它的作者（这就是为什么我有 ->with('user')）
回复数量（这就是为什么我有 >withCount(['posts AS approved_replies' => function ($query) { ...）

最新（最新）日期post及其作者。这就是为什么：

    ->with(['posts' => function ($query) { // Posts
        $query->approved()
            ->with('user') // Author of post
            ->latest(); // LATEST first
        }]
    )

... 因为在 index.blade.php 中我可以通过以下方式访问每个线程的最新 post：

@foreach ($threads as $thread) 
    {{ $thread->posts->first()->created_at; }}
    {{ $thread->posts->first()->user->username; }}
@endforeach

此代码的问题在于线程按它们的 created_at 排序，而不是按最近的 post 排序。我想实现的是按最新（最近）post来订购threads，但我不知道如何这样做。

Answer 1

您需要使用join():

$threads = Thread::join('posts as p', 'p.thread_id', '=', 'threads.id')
    ->where('forum_id', $this->forum->id)
    ->approved()
    ->withCount(['posts AS approved_replies' => function ($query) {
        $query->where('posts.approved', true)->where('posts.is_starting_thread', false);
    }])
    ->with(['posts' => function ($query) { // Posts
        $query->approved()
            ->with('user') // Author of post
            ->latest();
        }]
    )
    ->with('user') // Author of thread
    ->latest('p.created_at')
    ->paginate(20);

Answer 2

这是我的做法。它不是特别漂亮，但应该可以完成工作

$this->forum->threads()
    ->approved()
    ->join('posts', 'posts.thread_id', '=', 'threads.id')
    ->selectRaw('threads.*, MAX(posts.created_at) AS latest_post_at')
    ->groupBy('threads.id')
    ->orderByDesc('latest_post_at')
    ->withCount(['posts AS approved_replies' => function ($query) {
        $query->where('posts.approved', true)->where('posts.is_starting_thread', false);
    }])
    ->with(['posts' => function ($query) { // Posts
        $query->approved()
            ->with('user') // Author of post
            ->latest();
        }]
    )
    ->with('user')
    ->paginate(20);

它按照其他答案的建议执行 join，然后按线程 groups，使用 MAX 聚合函数来保持每组帖子的最新日期。

编辑：

$this->forum->threads()
    ->approved()
    ->join('posts', 'posts.thread_id', '=', 'threads.id')
    ->select('threads.*', 'posts.created_at AS latest_post_at')
    ->whereNotExists(function ($subquery) {
        return $subquery->from('posts AS later_posts')
            ->whereRaw('later_posts.thread_id = posts.thread_id')
            ->whereRaw('later_posts.created_at > posts.created_at');
    })
    ->orderByDesc('latest_post_at')
    ->withCount(['posts AS approved_replies' => function ($query) {
        $query->where('posts.approved', true)
              ->where('posts.is_starting_thread', false);
    }])
    ->with(['posts' => function ($query) { // Posts
        $query->approved()
            ->with('user') // Author of post
            ->latest();
    }])
    ->with('user')
    ->paginate(20);

按最新（最新）相关型号排序 [Laravel]

Order by the latest (most recent) related model [Laravel]

php

sql

laravel

laravel-5

laravel-eloquent

编辑：