如何使用雄辩平均多列？ [英] How to average multiple columns using Eloquent?

问题描述

我正在寻找相关模型的多个列的平均值，如下所示：

I'm looking to get the average value across multiple columns on a related model, something like this:

$this->reviews()->avg('communication', 'friendliness')

和友好是一列列名称。然而，它似乎聚合函数只支持单列名称，所以我这样做：

Where communication and friendliness are an array of column names. However it appears the aggregate functions only support single column names, so I'm doing this:

$attributes = array('communication', 'friendliness');
$score = array();

foreach ($attributes as $attribute)
{
    $score[] = $this->reviews()->avg($attribute);
}

return round(array_sum($score) / sizeof($attributes), 1);

哪些导致多个查询。任何关于最佳实践的建议在这里？

Which results in multiple queries. Any suggestions for a best practice here?

谢谢

推荐答案

避免多个查询，您可以在原始数据库表达式 doc / eloquent>口述，如下所示：

To avoid multiple queries you can use a raw database expression within Eloquent as shown below:

$averages = $this->reviews()
    ->select(DB::raw('avg(communication) c, avg(friendliness) f'))
    ->first();

echo $averages->c;
echo $averages->f;

由于集合函数名称 avg 已被识别由Laravel所有支持的数据库，这不会是一件大事。

Since the aggregate function name avg is recognized by all supported database by Laravel, this will not be a big deal.

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