复杂查询的问题（Laravel Eloquent）

Question

好久不见:D

最近，我一直在尝试开发一个网站，但似乎没有找到解决方案。已经3周了，我还做不到。 我没有使用模型，因为我仍然没有像我想要的那样理解它们，也许像 hasmany 或 belongsto 这样的东西会有所作为，但我不知道如何使用它们

---

这是查询：

$threads = DB::table('threads')
    ->join('users as author', 'author.id', '=', 'threads.user_id')
    ->join('replies', 'replies.thread_id', '=', 'threads.id')
    ->join('categories', 'categories.id', '=', 'threads.category_id')
    ->join('users as users', 'users.id', '=', 'replies.user_id')
    ->select('threads.id as thread_id','threads.category_id as thread_category','threads.title as thread_title', 'replies.body as thread_first_message', 'author.name as thread_author', 'author.id as author_id', 'replies.created_at as last_reply_date', 'users.name as last_reply_user', 'users.id as lru_id', 'threads.visits', 'threads.hd', 'threads.18', 'threads.prv', DB::raw('(SELECT COUNT(id) FROM replies WHERE thread_id = threads.id) as count_replies'))
    ->where('replies.created_at', '=', DB::raw('(SELECT max(created_at) FROM replies)'));

我需要从 3 个表中获取多个数据。

我将解释每一列的内容：

thread_id：来自表'threads'的字段（id）

thread_category：来自“threads”的字段（category_id）和来自表“categories”（id）的外键

thread_title：来自“线程”的字段（标题）

thread_first_message：第一个字段（正文）来自表 'replies' where thread_id = (thread_id)

thread_author：来自“threads”的字段（user_id）和来自表“users”的foregin key（id）

author_id：来自撰写第一条消息的“用户”的字段 (id)

last_reply_date：来自 'replies' 的字段 (created_at) 其中 'replies.id' = (thread_id)

last_reply_users：来自在 (thread_id) 中写入最后一条消息的“用户”的字段（名称）

lru_id：字段 (id) 来自 'users' 来自 'users'，最后一条消息写在 (thread_id)

visits：来自表“线程”的字段（访问）

hd, prv, 18：来自表“线程”的布尔字段（它们在这里无关紧要，也许在未来）

count_replies：所有回复的总和，其中 thread_id = (thread_id)

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数据库现在看起来像这样：

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我的问题是我在数据库中有2条记录，所以页面中应该显示2个div，但只显示一个：

我得到的结果：

我需要的结果：

因为threads表有2条记录：

你们能给我一些帮助吗？提前谢谢你

编辑：我到这里为止：

SELECT DISTINCT(t.id), t.category_id, t.title, r1.body, u1.name as author, u1.id, r2.created_at, u2.id as last_author_id, u2.name as last_author, t.visits, COUNT(DISTINCT(r3.id)) from threads t, replies r1, replies r2, replies r3, users u1, users u2 where r1.thread_id = t.id and u1.id = t.user_id and r2.thread_id = t.id and r2.user_id = u2.id and r3.thread_id = t.id group by t.id

它检索到这个：

我不知道如何将其转换为 Eloquent Query 或者它是否最佳

Answer 1

让我们以 Laravel 的方式来做。

首先，您应该创建模型。创建目录 app/Models 并将这些文件放在那里：

线程.php：

namespace App\Models;
use Illuminate\Database\Eloquent\Model;

class Thread extends Model {

  public function author() {
    return $this->belongsTo(User::class, 'user_id')
  }

  public function category() {
    return $this->belongsTo(Category::class, 'category_id')
  }

  public function replies() {
    return $this->hasMany(Reply::class, 'thread_id');
  }
}

用户.php：

namespace App\Models;
use Illuminate\Database\Eloquent\Model;

class User extends Model {

  public function threads() {
    return $this->hasMany(Thread::class, 'user_id')
  }

  public function replies() {
    return $this->hasMany(Reply::class, 'user_id')
  }

  public function votes() {
    return $this->hasMany(Vote::class, 'user_id')
  }
}

回复.php

namespace App\Models;
use Illuminate\Database\Eloquent\Model;

class Reply extends Model {

  public function thread() {
    return $this->belongsTo(Thread::class, 'thread_id')
  }

  public function author() {
    return $this->belongsTo(User::class, 'user_id')
  }

  public function votes() {
    return $this->hasMany(Vote::class, 'reply_id')
  }
}

Category.php

namespace App\Models;
use Illuminate\Database\Eloquent\Model;

class Category extends Model {

  public function threads() {
    return $this->hasMany(Thread::class, 'category_id')
  }
}

投票.php

namespace App\Models;
use Illuminate\Database\Eloquent\Model;

class Vote extends Model {

  public function author() {
    return $this->belogsTo(User::class, 'user_id')
  }

  public function reply() {
    return $this->belogsTo(Reply::class, 'reply_id')
  }
}

现在，给定一个 Thread，您可以轻松获得所需的结果

// last 10 threads
$threads = Thread::orderBy('created_at', 'desc')
   ->with('category')->limit(10)->get();

// You can loop on the blade template and display the informations you need
foreach($threads as $thread) {
  $thread->category->id; // The thread category ID
  $thread->category->name; // The thread category name

  $lastReply = $thread->replies()->orderBy('created_at', 'desc')->first(); // The last reply on the thread
  $lastReply->created_at; // Date of the latest reply
  $lastReply->author->name; // Name of the user that created the last reply

  $thread->visits; // The number of visits on the thread
  $repliesCount = $thread->replies()->count(); // Number of replies on the thread
}