Ruby on Rails：如何连接两个表
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Ruby on Rails: How to join two tables
提问by Max
I have an index page that I want to show all the users' profile and their associated photos. I'm using the plugin Paperclip for the photos. In the Profiles controller, I have the instance variable @profile but it shows me the table in the profiles table only and not the photos table.
我有一个索引页面，我想显示所有用户的个人资料及其相关照片。我正在为照片使用插件 Paperclip。在 Profiles 控制器中，我有实例变量 @profile 但它只向我显示了配置文件表中的表，而不是照片表。
@profile = Profile.find(:all, :include => :photos,
:joins => "INNER JOIN photos ON photos.profile_id = profiles.id")
The models are shown below:
模型如下所示：
class Profile < ActiveRecord::Base
has_many :photos
end
class Photo < ActiveRecord::Base
belongs_to :profile
end
What I want to be able to show in the View is something like:
我希望能够在视图中显示的内容类似于：
- John's profile (e.g., name, age, sex) - John's picture (e.g., only one picture shown)
- Mary's profile here - Mary's picture shown here
- Bob's profile here - Bob's picture shown here
- 约翰的个人资料（例如姓名、年龄、性别） - 约翰的照片（例如，仅显示一张照片）
- 此处显示玛丽的个人资料 - 此处显示玛丽的照片
- 此处是鲍勃的个人资料 - 此处显示鲍勃的照片
回答by Greg Campbell
I've edited my answer to reflect your extra comments.
我已经编辑了我的答案以反映您的额外评论。
First of all, you shouldn't need the :joinsparameter; :include => :photosshould handle the join "behind the scenes" for you.
首先，你不应该需要:joins参数；:include => :photos应该为您处理“幕后”加入。
Here's one way to do what you're asking about.
这是做你问的事情的一种方法。
(in the models)
（在模型中）
class Profile < ActiveRecord::Base
has_many :photos
has_one :primary_photo, :class_name => "Photo", :conditions => {:primary => true}
end
(in the controller)
（在控制器中）
@profiles = Profile.find(:all, :include => :primary_photo)
(in the view)
（在视图中）
<% @profiles.each do |profile| %>
Name: <%= profile.name %>
Age: <%= profile.age %>
Photo: <%= image_tag profile.primary_photo.url %>
<% end %>
