求助：分组后最新一条数据

public function index(Request $request)
{
    $category_id = $request->get(‘category_id’, 1);
    $old_user_order = $request->get(‘old_user_order’, 0);
    $old_user_name = $request->get(‘old_user_name’, ‘’);
    $start_time = $request->get(‘start_time’, ‘’);
    $end_time = $request->get(‘end_time’, ‘’);
    $scale_result = $request->get(‘scale_result’, ‘’);

    $query = scaleOldUserResult::query();

    $query->select(['id', 'old_user_id', 'scale_id', 'reasons_id', 'admin_user_id', 'final_result', 'created_at']);
    $query->with([
        'old_user:id,name,order,status',
        'scale:id,name,category_id',
        'admin_user:id,name',
        'reasons'
    ]);
    $query->whereHas('old_user', function ($query) use ($old_user_order, $old_user_name) {
        if ($old_user_order > 0) {
            $query->where('order', 'LIKE', '%' . $old_user_order . '%');
        }
        if($old_user_name){
            $query->where('name', 'LIKE', '%' . $old_user_name . '%');
        }
    });

    $query->whereHas('scale', function ($query) use ($category_id) {
        $query->where('category_id', $category_id);
    });

    if ($start_time && $end_time) {
        $query->whereBetween('created_at', [$start_time . ' 00:00:00', $end_time . ' 23:59:59']);
    } else if ($start_time && !$end_time) {
        $query->where('created_at', '>=', $start_time . ' 00:00:00');
    } else if (!$start_time && $end_time) {
        $query->where('created_at', '<=', $end_time . ' 23:59:59');
    }
    if($scale_result){
        $query->where('final_result', $scale_result);
    }
    $query->latest();
    if($category_id == 2) {
          $query->groupBy('scale_id');
    }
    $list = $query->pages($this->per_page);

    return succ($list);
}

$category_id=2 的进行了分组，想获取分组后的最新的一条数据，有没有大佬有什么比较好的方法
注：关联了 old_user、scale、admin_user、reasons 四张表，

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