查找具有关联的计数的所有记录大于零 [英] Find all records which have a count of an association greater than zero

问题描述

我试图做一些事情，我认为这将是简单，但它似乎不是。

I'm trying to do something that I thought it would be simple but it seems not to be.

我有了很多空位项目模型。

I have a project model that has many vacancies.

class Project < ActiveRecord::Base

  has_many :vacancies, :dependent => :destroy

end

我想获得所有具有至少1个空缺的项目。 我想是这样的：

I want to get all the projects that have at least 1 vacancy. I tried something like this:

Project.joins(:vacancies).where('count(vacancies) > 0')

但它说

的SQLite3 ::的SQLException：没有这样的列：空缺：选择项目*从项目INNER JOIN空缺ON空缺，PROJECT_ID=项目，ID。 WHE​​RE（项目deleted_atIS NULL。）和（计数（空缺）大于0）。

推荐答案

加入默认情况下使用，以便使用内部连接 Project.joins（：休假）将生效只返回有关联的度假项目。

joins uses an inner join by default so using Project.joins(:vacations) will in effect only return projects that have an associated vacation.

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