我有3个表，它们之间有多对多的关系，现在如何在laravel中使用mysql来获取数据

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class User extends Model
{
    protected $table = 'users';

    public function roles()
    {
        return $this->belongsToMany(Role::class, 'role_user');
    }
}

class Role extends Model
{
    protected $table = 'roles';

    public function users()
    {
        return $this->belongsToMany(User::class, 'role_user');
    }
}

class RoleUser extends Model
{
    protected $table = 'role_user';
}

$user = User::find(1);
$roles = $user->roles;

$role = Role::find(1);
$users = $role->users;

$user = User::find(1);
$roles = $user->roles()->withPivot('column1', 'column2')->get();

$role = Role::find(1);
$users = $role->users()->withPivot('column1', 'column2')->get();

$userRoles = DB::table('users')
                ->join('role_user', 'users.id', '=', 'role_user.user_id')
                ->join('roles', 'role_user.role_id', '=', 'roles.id')
                ->where('users.id', 1)
                ->select('roles.*')
                ->get();

$roleUsers = DB::table('roles')
                ->join('role_user', 'roles.id', '=', 'role_user.role_id')
                ->join('users', 'role_user.user_id', '=', 'users.id')
                ->where('roles.id', 1)
                ->select('users.*')
                ->get();