使用联接的Ruby on Rails ActiveRecord查询 [英] Ruby on Rails ActiveRecord query using a join

问题描述

我有一个用户模型，该用户具有has_many pets的关系。我希望能够编写一个ActiveRecord查询，在其中可以选择所有拥有不带pet的宠物的用户。名称为蓬松

I have a User model and the user has a relationship which is has_many pets. I want to be able to write an ActiveRecord query where I can select all users with a pet that doesn't have a pet.name of "fluffy"

什么是最ActiveRecord编写此有效的方法？使用简单的SQL看起来像以下内容：

What's the most efficient way to write this using ActiveRecord? Using straight SQL it would look something such as the following:

从用户中选择ID INNER JOIN pets on u.id = pets.user_id WHERE pets .name！=蓬松

推荐答案

这应该有效：

User.joins(:pets).where("pets.name != 'fluffy'")

另外，您可能需要阅读下一部分（在 joins 上），遵循官方RoR指南。

Also you might want to read the following part (on joins) on the official RoR guidelines.

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