Rails-仅查找存在has_many相关记录的记录 [英] Rails - only find records where has_many associated records are present

问题描述

我有一个与其他模型具有 has_many 关系的模型，

I have a model with a has_many relation with another model like so:

class Parent < ActiveRecord::Base
  has_many :children
end

class Child < ActiveRecord::Base
  belongs_to :parent
end

由于有些父母可能没有孩子，所以我想执行一个查询，该查询仅返回确实有孩子的父母.我将如何处理这样的事情?

Since there are some parents that may not have children, I'd like to do a query that returns only the parents that DO have children. How would I go about something like this?

由于我是在Rails 3上执行此操作的，因此如果此查询不使用 where.not.语法，将会很有帮助.

Since I'm doing this on Rails 3, it would be helpful if this query were to not use the where.not. syntax.

推荐答案

路轨4

Parent.includes(:child).where.not(children:{id:nil})

或

Parent.joins(:child).distinct

Parent.joins(:child).distinct

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