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POFiltering Django Query by the Record with the Maximum Column Value
 

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  1. POFiltering Django Query by the Record with the Maximum Column Value
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    <p>Is there an easy way to filter a Django query based on which record has a max/min value in a column? I'm essentially asking <a href="https://stackoverflow.com/questions/586781/postgresql-fetch-the-row-which-has-the-max-value-for-a-column">these</a> <a href="https://stackoverflow.com/questions/121387/fetch-the-row-which-has-the-max-value-for-a-column/123511#123511">questions</a>, but in the specific context of Django's ORM.</p> <p>e.g.</p> <p>Say I have a model designed to store the historical values of everyone's phone numbers.</p> <pre><code>class Person(models.Model): name = models.CharField(max_length=100) phone = models.CharField(max_length=100) created = models.DateTimeField(auto_now_add=True) </code></pre> <p>with the records:</p> <pre><code>Person(name='Jim',phone='123-456-9870', created=datetime(2005,1,2,4,2)) Person(name='Jim',phone='329-802-9870', created=datetime(2006,9,2,7,8)) Person(name='Sue',phone='324-345-3450', created=datetime(2008,7,4,6,1)) </code></pre> <p>Now say I wanted to find everyone's most recent phone number.</p> <p>In SQL, I'd usually have to use a subquery to calculate the maximum values:</p> <pre><code>SELECT p1.name, p1.phone, p1.created FROM person_person p1, ( SELECT name, MAX(created) AS max_created FROM person_person GROUP BY name ) AS p2 WHERE p1.name = p2.name AND p1.created = p2.max_created </code></pre> <p>Is there any mechanism in Django that could simplify this?</p> <p>I'm using PostgreSQL on my backend, so any thoughts or solutions that would rely on PostgreSQL specific functionality would be helpful.</p>
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    1. COIts seems that on django you can't do what you are looking for unless you use a raw query sql. check [this](https://docs.djangoproject.com/en/dev/ref/models/querysets/#distinct). Since at the moment you add an order_by('created') that created is added to the select in the query, the distinct will do nothing.
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