laravel 如何使用 Builder“按...排序”一个 Eloquent 关系
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How to "order by ..." an Eloquent relationship using Builder
提问by Eduardo Kasper
I have to order a query, from a relationship in Laravel 4. There are two Models: Taskand Subproject.
我必须从 Laravel 4 中的关系中订购一个查询。有两个模型：Task和Subproject。
In TaskI have a relationship with Subproject. This way:
在Task我与Subproject. 这边走：
public function subproject()
{
return $this->belongsTo('Subproject');
}
From my Controller, I want to order Subprojectusing Laravel Builderand not joins.
从我的Controller，我想订购Subproject使用Laravel Builder而不是加入。
Is there a way to do it?
有没有办法做到这一点？
采纳答案by Alexandre Butynski
What you want to do is is eager loading. Load a model and it's linked model in a single request. You can do this with the Eloquent::with()method, like that :
您要做的是预先加载。在单个请求中加载模型及其链接模型。您可以使用该Eloquent::with()方法执行此操作，如下所示：
$subprojects = Subproject::with('task')->orderBy('subproject.id')->get();
Then you get a list of subprojects with, in memory, the linked tasks and you can call tasks without anymore SQL request :
然后你会得到一个子项目列表，在内存中，链接的任务，你可以在没有 SQL 请求的情况下调用任务：
foreach($subprojects as $project) {
echo $project->task->id;
}
回答by The Alpha
From the comment :
从评论：
I want to order based on a parent table. Like that: select subprojects.id, tasks.id from tasks join subprojects on tasks.subproject_id = subprojects.id order by subprojects.id
我想根据父表订购。像这样：选择subprojects.id，tasks.id从tasks join subprojects on tasks.subproject_id = subprojects.id order by subprojects.id
It could be achived using following :
可以使用以下方法实现：
DB::table('tasks')
->join('subprojects', 'tasks.subproject_id', '=', 'subprojects.id')
->order_by('subprojects.id', 'ASC') // DESC
->select('subprojects.id,', 'tasks.id')
->get(); // for pagination you can use: ->paginate(5)
