Rails ActiveRecord: PG:::Error:列引用“created_at”是不明确的

I am struggling with the error in object and not sure at all where is the problem.

我正在与对象中的错误作斗争，完全不确定问题在哪里。

This is how the models looks like:

模型是这样的:

class Car < ActiveRecord::Base  
  has_many :car_colors
  has_many :colors, :through => :car_colors
end

class CarColor < ActiveRecord::Base
  belongs_to :color
  belongs_to :car
end

class Color < ActiveRecord::Base  
  has_many :car_colors
  has_many :cars, :through => :car_colors
end

Here is the query:

在这里查询:

@cars = Car.all(:joins => :car_colors, :conditions => { :car_colors => {:color_id => params[:id_number]}}, :order => "cars.created_at DESC")

And the error output:

和错误输出:

PG::Error: ERROR:  column reference "created_at" is ambiguous
LINE 1: ...d" WHERE "car_colors"."color_id" = 2 AND (created_at...
                                                             ^
: SELECT "cars".* FROM "cars" INNER JOIN "car_colors" ON "car_colors"."car_id" = "cars"."id" WHERE "car_colors"."color_id" = 2 AND (created_at > '2013-05-03 12:28:36.551058') ORDER BY cars.created_at DESC

The generated SQL query (below the error message) seems to be fine, but what causes the error message?

生成的SQL查询(错误消息下面)看起来不错，但是是什么导致了错误消息?

Thank you in advance.

提前谢谢你。

3 个解决方案

#1

There likely is a created_at field in your car_colors table. created_at should probably be cars.created_at to remove the ambiguity.

您的car_colors表中可能有一个created_at字段。created_at应该是汽车。created_at消除歧义。

#2

Define a scope like this:

定义一个这样的范围:

scope :scope_age, -> { order(created_at: :desc) }

rather than:

而不是:

scope :scope_age, -> { order("created_at DESC") }

It removes the ambiguity by using the property of the model in which the scope is defined in.

它通过使用定义范围的模型的属性来消除模糊性。

#3

Don't remove your timestamps from the join model, they aren't the problem - the problem is that something is adding a condition to your query:

不要从连接模型中删除时间戳，它们不是问题所在——问题是有些东西在向查询添加条件:

AND (created_at > '2013-05-03 12:28:36.551058')

Since the date is one month ago, search your code for one.month.ago and see if it appears in any scopes, probably in your cars or car_colors models. Check the scopes manually if nothing turns up through the search.

因为日期是一个月前，所以搜索你的代码一个月。看看它是否出现在任何范围内，可能出现在您的汽车或car_colors模型中。如果搜索没有出现任何结果，请手动检查范围。

Removing the timestamps will make your query work, but it's not the right thing to do.

删除时间戳将使查询有效，但这不是正确的做法。

#1