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copied!<p>The canonical way to do this with Rails 3:</p> <pre><code>Foo.includes(:bar).where("bars.id IS NOT NULL") </code></pre> <p>ActiveRecord 4.0 and above adds <a href="http://edgeguides.rubyonrails.org/active_record_querying.html#not-conditions" rel="noreferrer"><code>where.not</code></a> so you can do this:</p> <pre><code>Foo.includes(:bar).where.not('bars.id' => nil) Foo.includes(:bar).where.not(bars: { id: nil }) </code></pre> <p>When working with scopes between tables, I prefer to leverage <a href="http://api.rubyonrails.org/classes/ActiveRecord/SpawnMethods.html#method-i-merge" rel="noreferrer"><code>merge</code></a> so that I can use existing scopes more easily.</p> <pre><code>Foo.includes(:bar).merge(Bar.where.not(id: nil)) </code></pre> <p>Also, since <a href="http://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-includes" rel="noreferrer"><code>includes</code></a> does not always choose a join strategy, you should use <a href="http://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-references" rel="noreferrer"><code>references</code></a> here as well, otherwise you may end up with invalid SQL.</p> <pre><code>Foo.includes(:bar) .references(:bar) .merge(Bar.where.not(id: nil)) </code></pre> <p>I no longer recommend using <a href="https://github.com/activerecord-hackery/squeel" rel="noreferrer">Squeel</a> for this as it doesn't always have a full-time maintainer, and it depends on private APIs that cause frequent breaking changes.</p>

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