具有三级深度连接的作用域 [英] Scope that has three levels deep joins

问题描述

我的Program表有很多Measures我的 Measure 表有很多 Targets我的 Target 表有一列名为money"

My Program table has many Measures My Measure table has many Targets My Target table has a column called "money"

我的 ActiveRecord 查询如下所示:

My ActiveRecord query looks like this:

@programs2 = Program.includes([measures: :target]).where('organization_id = 1').limit(2)

我想定义一个范围，以便查询可以返回其 target.money 值最低的顶级程序.因此，我需要编写一个范围并将其应用于该查询，但是我应该如何以及在模型中的何处定义该范围，像这样?好吧，这行不通，但我知道的就这么多.

I want to define a scope such that the query can return top Programs that their target.money value is the lowest. So I need to write a scope and apply it to that query but How and Where in the model should I define that scope, something like this? Well this won't work but that's as much as I know.

scope :top5, :joins => [:measures, :targets]  ,  :order => "money DESC"

推荐答案

一个 Program 的 target.money 是多少，这个 Program 的所有 Measures 的所有 Targets.money 的总和?

What is the target.money of a Program, the sum of all Targets.money of all Measures for this Program ?

您可以尝试以下操作:

Target.order_by( :money => :desc ).map{|target| target.measure }.map{|measure| measure.program }.uniq

祝你好运

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