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PORails 3: ActiveRecord query with :includes only returns results that have related values in included table?
 

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  1. PORails 3: ActiveRecord query with :includes only returns results that have related values in included table?
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    <p>I've got a model (a <code>Feature</code>) that can have many <code>Assets</code>. These <code>Assets</code> each have an <code>issue_date</code>. I'm struggling with what seems like a simple ActiveRecord query to <strong>find all <code>Features</code> and their <code>Assets</code> with an <code>issue_date</code> of tomorrow, regardless of if there are <code>Assets</code> or not</strong> — preferably with one query.</p> <p>Here's my query right now.</p> <pre><code>Feature.includes(:assets).where(:assets =&gt; { :issue_date =&gt; Date.tomorrow }) </code></pre> <p>Unfortunately, this returns only the <code>Features</code> that have <code>Assets</code> with an <code>issue_date</code> of tomorrow. Even stranger, the generated SQL looks like this (tomorrow's obviously the 19th).</p> <pre><code>SELECT `features`.* FROM `features` WHERE `assets`.`issue_date` = '2011-08-19' </code></pre> <p>Shouldn't this have an <code>LEFT JOIN</code> in there somewhere? That's the sort of thing I'm going for. Using <code>joins</code> instead of <code>includes</code> does an <code>INNER JOIN</code>, but that's not what I want. Strangely enough, it seems like I'm getting an <code>INNER JOIN</code>-type of behavior. When I run that <code>includes</code> query above, the actual SQL that's spit out looks something like this...</p> <pre><code>SELECT `features`.`id` AS t0_r0, `features`.`property_id` AS t0_r1, // every other column from features truncated for sanity `assets`.`feature_id` AS t1_r1, `assets`.`asset_type` AS t1_r2, // all other asset columns truncated for sanity FROM `features` LEFT OUTER JOIN `assets` ON `assets`.`feature_id` = `features`.`id` WHERE `assets`.`issue_date` = '2011-08-19' </code></pre> <p>Which <strong>looks</strong> like it should work right but it doesn't. I get <em>only</em> the <code>Features</code> that have <code>Assets</code> with an <code>issue_date</code> of tomorrow. Any idea what I'm doing wrong?</p> <p>I've tried the older, Rails v2 way of doing it…</p> <pre><code>Feature.find(:all, :include =&gt; :assets, :conditions =&gt; ['assets.issue_date = ?', Date.tomorrow]) </code></pre> <p>Which gives me the same results. There's one <code>Feature</code> I know that doesn't have any <code>Assets</code> for tomorrow, and it's not in that list.</p> <p>I've also poked around and found similar questions, but I couldn't seem to find one that explained this opposite behavior I'm seeing.</p> <p><strong>Edit</strong>: I'm <em>so</em> close. This gets me all the <code>Feature</code> objects.</p> <pre><code>Feature.joins("LEFT OUTER JOIN assets on assets.feature_id = feature.id AND asset.issue_date = #{Date.tomorrow}") </code></pre> <p>It does <strong>not</strong>, however, get me the matching <code>Assets</code> bundled into the object. With <code>feature</code> as a returned item in the query, <code>feature.assets</code> makes another call to the database, which I don't want. I want <code>feature.assets</code> to return only those I've specified in that <code>LEFT OUTER JOIN</code> call. What else do I need to do to my query?</p>
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    1. COIf issue_date is a field in the asset table, how are you expecting a query for a specific issue_date to ever return a feature that doesn't have any assets?
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    2. COI apologize if my post isn't clear in that regard. I want a list of all `Features` as well as `Assets` for a certain date **if** such `Assets` exist; otherwise, just the `Feature`.
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    3. COOh sorry I understand, you did explain it but I think I got lost reading the rails-generated query. The issue_date is a query for the outer join, rather than a query on the result set.
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