Laravel:计算关系中的行数 [英] Laravel: Count number of rows in a relationship

问题描述

我有以下关系:

• 一个场馆有很多优惠
• 要约有很多订单

我有以下雄辩的模型来表示这一点:

I have the following Eloquent model to represent this:

class Venue {
    public function orders()
    {
        return $this->hasManyThrough(Order::class, Offer::class);
    }
}

我想使用Laravel的Eloquent模型确定location_id = 5场所的订单总数.

I want to determine the total number of orders for venues with location_id = 5 using Laravel's Eloquent model.

我设法做到这一点的唯一方法如下:

The only way I managed to do this is as follows:

$venues = Venue::where('location_id', 5)->with('orders')->get();

$numberOfOrders = 0;
foreach($venues as $venue) {
    $numberOfOrders += $venue->orders->count();
}
dump($numberOfOrders); // Output a single number (e.g. 512)

但是，这显然不是很有效，因为我使用PHP而不是SQL来计算计数.

However, this is obviously not very efficient as I am calculating the count using PHP instead of SQL.

如何单独使用Eloquent模型来做到这一点.

How can I do this using Eloquent model alone.

推荐答案

您可以使用Eloquent.从Laravel 5.3开始，存在withCount().

You can use Eloquent. As of Laravel 5.3 there is withCount().

根据您的情况，您将拥有

In your case you will have

$venues = Venue::where('location_id', 5)->with('orders')->withCount('orders')->get();

然后以这种方式访问​​

Then access it this way

foreach ($venues as $venue) {
    echo $venue->orders_count;
}

可以在此处找到参考: https://laravel.com/docs/5.3 /eloquent-relationships#querying-relations

Can find reference here: https://laravel.com/docs/5.3/eloquent-relationships#querying-relations

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