AAAs.includes(:BBBs) # 子 AAAs.includes(BBBs: :CCCs) # 孫 AAAs.includes(:GGGs, BBBs: [:CCCs, :DDDs]) # 子と孫たち AAAs.joins(BBBs: [{CCCs: :FFFs}, :DDDs]) # ひ孫もあるとこう 参考 Ruby on Rails - 用 Include 和 Join 避免 N+1 Query | Leon's Blogging https://mgleon08.github.io/blog/2016/01/10/ruby-on-rails-include-join-avoid-n-1-query/ Rails ActiveRecord/SQL 小技集 | Qiita https://qiita.com/tomomomo1217/items/1ccd21bfb977307