ActiveRecord查询has_many:通过模型

Question

如何在"has_many:through"关系中查询具有特定分支的公司？

  #company.rb
  has_many :branch_choices
  has_many :branches, :through => :branch_choices

"查找所有分行ID为3的公司"

Answer 1

Company.includes(:branches).where(:branches => {:id => 3})

要么

Branch.find(3).companies

更新 实际上,第一个片段有一个缺点:它急切地加载分支机构和公司.为避免这种开销,您可以考虑使用左连接:

Company.
  joins("LEFT JOIN `branch_choices` ON `branch_choices`.`company_id` = `companies`.`id`").
  where(:branch_choices => {:branch_id => 3})