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PORails 3 ActiveRecord query
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  1. PORails 3 ActiveRecord query
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    copied!<p>Given a Rails 3 app with the following models:</p> <pre class="lang-rb prettyprint-override"><code># == Schema Information # Schema version: 20110517144920 # # Table name: orders # # id :integer not null, primary key # user_id :integer not null # name :string(255) not null # state :string(255) # created_at :datetime # updated_at :datetime # class Order &lt; ActiveRecord::Base belongs_to :user has_many :multipage_pdfs, :as =&gt; :assetable, :dependent =&gt; :destroy has_many :singlepage_pdfs, :as =&gt; :assetable, :dependent =&gt; :destroy ... end # == Schema Information # Schema version: 20110511064747 # # Table name: assets # # id :integer not null, primary key # assetable_id :integer not null # assetable_type :string(255) not null # state :string(255) # type :string(255) not null # name :string(255) not null # document :string(255) not null # version :integer default(0), not null # created_at :datetime # updated_at :datetime # class Asset &lt; ActiveRecord::Base ... end class SinglepagePdf &lt; Asset ... end </code></pre> <p>asset#version is increased each time a new asset is created, if an asset with an identical name exists, so that's what my assets typically look like (simplified):</p> <pre> | id | assetable_id | assetable_type | name | version | type | | 1 | 1 | Order | my.pdf | 1 | SinglepagePdf | | 2 | 1 | Order | my.pdf | 2 | SinglepagePdf | | 3 | 1 | Order | my.pdf | 3 | SinglepagePdf | | 4 | 1 | Order | bla.pdf | 1 | SinglepagePdf | </pre> <p>Now i need to get all singlepage_pdfs of a single order, but only the last version for each name. How can i achieve this?</p> <pre class="lang-rb prettyprint-override"><code>o = Order.find(1) singlepage_pdfs = o.singlepage_pdfs.find(...) </code></pre> <p>The result should contain only contain the Assets with id 3 and 4...</p>
 

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