如何使用ActiveRecord和POSTGRES平均产品评论评分 [英] How to average product review scores using activerecord and POSTGRES

问题描述

假设我有一张桌子，上面有100条商品评论。每个评论都有一个 id， product_id和 score。现在，我想做的是呈现每种产品的平均得分...那么有没有办法使用Rails来查询数据库呢？我确定一定有，但我无法弄清楚。我希望发生以下情况：

Let's say I have a table with 100 product reviews. Each review has an "id", "product_id", and "score". Now, what I want to do is present the average score for each product... So is there a way to query the DB using Rails to do this? I'm sure there must be, but I can't figure it out. I would like the following to occur:

Toyota Corolla 70%
Toyota Camry 78%
Toyota Avalon 80%

..显然是基于对每个评价的平均数，但是以上述方式呈现。

.. obviously based on multiple reviews for each that are averaged, but presented in the above fashion.

更新：

对于那些对解决方案感兴趣的人

For those interested in the solution

这是在控制器中：

@ordered_hash = Review.group('aidmodel_id').average('score')
@keys = @ordered_hash.keys
@reviews = Review.where(:aidmodel_id=>@keys).uniq_by {|x| x.aidmodel_id}

在视图中：

<% @reviews.each do |review| %>

    <%= review.aidmodel.id %>
    <%= @ordered_hash[review.aidmodel_id] %>

  <% end %>

@ordered_hash [review.aidmodel_id]

推荐答案

您可以混合使用平均值和 group 做类似的事情

You can mix average and group to do something like

MyClass.group('product_id').average('score')
# => {product_id1 => average1, product_id2 => average2, ... }

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