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POadvanced (nexted) has_many :through queries in Ruby on Rails (double-JOIN)
 

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  1. POadvanced (nexted) has_many :through queries in Ruby on Rails (double-JOIN)
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    <p>I am having a somewhat too nested database layout, however, I seem to need it. That is, Our website visitors may each have a single account with maintaining multiple users (think of identities) within. Now they may create tickets, which are grouped by ticket sections, and we have ticket manager (operator) to process the incoming tickets. Not every ticket manager may see every ticket but only those this manager is a member of the given ticket section for.</p> <p>Now, I am totally fine in querying via raw SQL statements, but I failed to verbalizing those two special queries the Rails way.</p> <p>Here is the (abstract) model:</p> <pre><code># account system class Account &lt; ActiveRecord::Base has_many :users has_many :tickets, :through =&gt; :users has_many :managing_ticket_sections, ... # TicketSection-collection this account (any of its users) is operate for has_many :managing_tickets, ... # Ticket-collection this account (any of its users) may operate on end class User &lt; ActiveRecord::Base belongs_to :account has_many :tickets has_many :managing_ticket_sections, ... # TicketSection-collection this user is operate for has_many :managing_tickets, ... # Ticket-collection this user may operate on end # ticket system class Ticket &lt; ActiveRecord::Base belongs_to :author, :class_name =&gt; "User" belongs_to :assignee, :class_name =&gt; "User" belongs_to :section, :class_name =&gt; "TicketSection" end class TicketSection &lt; ActiveRecord::Base has_many :tickets has_many :operators end class TicketSectionManager &lt; ActiveRecord::Base belongs_to :manager, :class_name =&gt; "User" belongs_to :section end </code></pre> <p>I am aware of basic <code>has_many :through</code>-constructs, however, here, I am accessing more than three tables to get the tickets.</p> <p>Something that actually works for in the User's model is:</p> <pre><code>class User &lt; ActiveRecord::Base has_many :managing_relations, :class_name =&gt; "TicketSectionManager" # XXX some kind of helper, for the two below has_many :managing_sections, :class_name =&gt; "TicketSection", :through =&gt; :managing_relations, :source =&gt; :section has_many :managing_tickets, :class_name =&gt; "Ticket", :through =&gt; :managing_relations, :source =&gt; :section end </code></pre> <p>Here I am using a helper relation (<code>managing_relations</code>), which is absolutely never used except by the two has_many relations below. I were not able to describe a User.managing_sections nor User.managing_tickets relation without this helper, which is, where I need an advice for.</p> <p>Secondly, the customer is to have a look at all of the tickets he can manage on <em>any</em> User (think of an identity) he has logged in, so what I need, is a way to collect all tickets (/sections) this Account is permitted to manage (identified by being a member of the corresponding TicketSection)</p> <p>Here I even were not able to express this relation the ruby way, and I had to work around it by the following:</p> <pre><code>class Account def managing_tickets Ticket.find_by_sql("SELECT t.* FROM tickets AS t INNER JOIN ticket_section_managers AS m ON m.section_id = t.section_id INNER JOIN users AS u ON u.id = m.user_id WHERE u.account_id = #{id}") end end </code></pre> <p>I'd appreciate any kind of advice, and many thanks in advance, Christian Parpart.</p>
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