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POSequel - Query Many to Many Associations
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  1. POSequel - Query Many to Many Associations
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    copied!<p>I am having issues constructing the proper models, associations, and query for the following scenario and then returning results as JSON using Sequel with Ruby.</p> <p>The database structure___</p> <p>You can create a list of books. Each library contains books. Defined by the following:</p> <pre><code>db.create_table(:books) do primary_key :id String :name String :author DateTime :created end db.create_table(:libraries) do primary_key :id String :name String :city String :state DateTime :created end db.create_table(:libraries_books) do Integer :library_id Integer :book_id primary_key [:library_id, :book_id] end class Library &lt; Sequel::Model(:libraries) many_to_many :libraries_books, :left_key=&gt;:library_id, :right_key=&gt;:book_id, :join_table=&gt;:libraries_books one_to_many :libraries_books, :key=&gt;:library_id end class LibraryBook &lt; Sequel::Model(:libraries_books) many_to_one :libraries many_to_one :books end </code></pre> <p>I am trying to determine the correct way to access all the book names for a given library. I initially tried to follow the Sequel Associations guide but was not able to figure out how I could use LibraryBook with associations to get all the books for a library and join on the Book model to get the proper columns.</p> <p>After getting stuck with some of the methods described, I attempted to create my own query as such:</p> <pre><code>LibraryBook.select(:books.*) .join_table(:inner, :libraries, :id =&gt; :library_id) .join_table(:inner, :books, :id =&gt; :book_id) .where(:library_id =&gt; 1) </code></pre> <p>Which seems to get me partially there. However, when I use the serialization extension, I get an error when the results are being converted:</p> <pre><code>undefined method `book_id' for #&lt;LibraryGame:0x007fa9e904b470&gt; </code></pre> <p>Any insight into that can be provided would be very helpful!</p>
 

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