Rails 按 has_many 关联的结果计数排序 [英] Rails order by results count of has_many association

问题描述

无论如何我可以通过从子模型(Jobs)返回的项目数对结果(ASC/DESC)进行排序?

Is there anyway I can order the results (ASC/DESC) by number of items returned from the child model (Jobs)?

@featured_companies = Company.joins(:jobs).group(Job.arel_table[:company_id]).order(Job.arel_table[:company_id].count).limit(10)

例如:我需要将职位最高的公司打印在顶部

For example: I need to print the Companies with highest jobs on top

推荐答案

如果你希望经常使用这个查询，我建议你使用内置的 counter_cache

If you expect to use this query frequently, I suggest you to use built-in counter_cache

# Job Model
class Job < ActiveRecord::Base
  belongs_to :company, counter_cache: true
  # ...
end

# add a migration
add_column :company, :jobs_count, :integer, default: 0

# Company model
class Company < ActiveRecord::Base
  scope :featured, order('jobs_count DESC')
  # ...
end

然后像这样使用

@featured_company = Company.featured

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