Ruby-on-rails Rails：基于关联值的 ActiveRecord 查询
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Rails: ActiveRecord query based on association value
提问by user2158382
I have 2 models. Reportand Serverthat have a belongs_to and has_many relationship. I created an accessor method using delegatethat allows a Reportto find its associated Server.company_id. Now, I want to run a query on Reportthat allows me to find all Reportthat are associated with a specific Serverthat has a specific company_idattribute of 5.
我有2个模型。Report并且Server有一个belongs_to 和has_many 关系。我创建了一个访问器方法delegate，它允许 aReport找到其关联的Server.company_id. 现在，我想运行一个查询Report，让我可以找到Report与Server具有特定company_id属性 5的特定关联的所有内容。
Here are my two models. And yes I know the current query wont work since Reportdoes not have an attribute company_id.
这是我的两个模型。是的，我知道当前查询不起作用，因为Report没有属性company_id。
And no, I dont want to store company_idinside of Reportsince that information doesn't belong in Report.
不，我不想存储company_id在里面，Report因为该信息不属于Report.
Report
报告
class Report < ActiveRecord::Base
belongs_to :server
delegate :company_id, :to => :server
class << self
def method(url, base_url)
#Report.where(company_id: 5)
end
end
end
Server
服务器
class Server < ActiveRecord::Base
attr_accessible :company_id
has_many :reports
end
回答by KappaNossi
You can perform a query like this:
您可以执行如下查询：
Report.joins(:servers).where(:servers => {:company_id => 5})
To me, this is the cleaner solution to raw SQL.
对我来说，这是原始 SQL 的更干净的解决方案。
回答by Joseph Gill
I'm using Rails 4.1.7 and the accepted answer did not work for me. What did work is
我正在使用 Rails 4.1.7，但接受的答案对我不起作用。什么工作是
Report.joins(:server).where(:servers => {:company_id => 5})
Note that the difference is the key in the where clause is pluralized (:servers instead of :server)
请注意，区别在于 where 子句中的关键是复数形式（:servers 而不是 :server）
回答by Patrick Oscity
This should do the trick
这应该可以解决问题
Report.joins(:server).where('servers.company_id = ?', 5)
you could also add a scope for this like so
你也可以像这样添加一个范围
scope :with_company_id, lambda {|id| joins(:server).where('servers.company_id = ?', id) }
and then write
然后写
Report.with_company_id(5)
回答by nroose
Server.where(company_id: 5).first.reports
Server.where(company_id: 5).first.reports
