如何使用Laravel和Eloquent查询具有多个关系的数据透视表

Question

In Laravel 5, I have a database with the following schema:

| USERS    | JOBS  | CONVERSATIONS | MESSAGES        | CONVERSATION_USER |
| id       | id    | id            | id              | user_id           |
| username | title | job_id        | conversation_id | conversation_id   |
| password |       |               | user_id         |                   |
|          |       |               | message         |                   |

Where my conversation_user table is a pivot table.

Exam Question: I'm trying to use the conversation_user pivot table to obtain all of the conversation_ids relating to the logged in user and then use those results to get the last message relating to that conversation as well as the title of the job the conversations relate to.

In SQL terms this equates to:

SELECT t1.message, t2.title FROM

(SELECT messages.`message`, messages.conversation_id FROM conversation_user
INNER JOIN messages ON conversation_user.conversation_id=messages.conversation_id
WHERE conversation_user.user_id=$user_id ORDER BY messages.id DESC) t1

INNER JOIN

(SELECT jobs.`title`, conversations.id FROM conversations INNER JOIN jobs ON
conversations.job_id=jobs.id) t2

ON t1.conversation_id=t2.id

However I cannot figure out how to achieve this with Eloquent!

My relationships are below:

User model:
$this->hasMany('job');
$this->hasMany('message');
$this->belongsToMany('conversation');

Job model:
$this->belongsTo('user');
$this->hasMany('conversation');
$this->hasManyThrough('message', 'conversation');

Conversation model:
$this->belongsTo('job');
$this->hasMany('message');
$this->belongsToMany('user');

Message model:
$this->belongsTo('user');
$this->belongsTo('conversation');

Answer 1

If I undestood correctly, this is what you need

    $user = User::find(Auth::id());
    foreach($user->conversations()->with('messages', 'job')->get() as $conversation)
    {
        echo $conversation->job->title;
        echo $conversation->messages->sortBy('id')->last()->message;
    }