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    <p>I'm afraid ShivamD's answer will not suffice. That would require duplicate <code>Skills</code>, and queries the relevant <code>User.help_requests</code> via relationship, where instead you need an intersection.</p> <p>Not just that, <code>Users</code> who create <code>HelpRequests</code> will already have a <code>has_many</code> relationship. That makes sense.</p> <p>I won't include schema for the <code>HABTM</code> I'm about to suggest (see <a href="http://guides.rubyonrails.org/association_basics.html#the-has-and-belongs-to-many-association" rel="nofollow">here</a>), but I will cover the models. Essentially what you want:</p> <pre><code>skill = Skill.create(name: "My Skill") user.skills &lt;&lt; skill help_request.skills &lt;&lt; skill user.matched_help_requests #&gt; [help_request] </code></pre> <p>Which can be achieved as follows:</p> <pre><code>class User has_and_belongs_to_many :skills def matched_help_requests HelpRequest.joins(:skills).where("skills.id IN(?)", skills.pluck(:id)) end end class HelpRequest has_and_belongs_to_many :skills end class Skill has_and_belongs_to_many :users has_and_belongs_to_many :help_requests end </code></pre> <hr> <p>EDIT: here's the schmea for the <code>HABTM</code>:</p> <pre><code>rails g migration add_skills_join_tables </code></pre> <h3>within migration</h3> <pre><code>def change create_table :skills_users, id: false do |t| t.references :skill t.references :user end create_table :help_requests_skills, id: false do |t| t.references :skill t.references :help_request end add_index :skills_users, [:skill_id, :user_id] add_index :help_request_skills, [:skill_id, :help_request_id] end </code></pre>
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    1. POA Ruby on Rails has_many relationship.
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    1. USDamien Roche
    1. USDamien Roche
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    1. POA Ruby on Rails has_many relationship.
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    1. COJust to clarify. As I'm setting up my HABTM relationships do I create one or two join tables without a primary key? (as indicated in the documentation) Also, would you mind explaining the "matched_help_request" method just a little bit more? Thanks a ton Damien, I appreciate it a lot.
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      1. USFlint285
    2. CO@Flint285 You'll require two join tables. See tiagotex's answer. The two tables you'll need are `skills_users` and `help_requests_skills`, and neither have a primary key, but they do have indexes. I'll update my answer to show the migration.
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    3. CO@Flint285 updated answer. The `matched_help_request` method could possibly be improved. What this does is collect the user's skill ids via the join table skills_users (`skills.pluck(:id)`), then performs a join query where `HelpRequest` skill ids match.
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