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PODjango "extra" query
 

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    <p>I have the following model structure in my models.py, with Items and Offers:</p> <pre><code>class Item(models.Model): STATUS_CHOICES = ( ('A', 'Active'), ('C', 'Cancelled'), ) status = models.CharField(max_length=11, choices=STATUS_CHOICES) target_amount = models.PositiveIntegerField() ... class Offer(models.Model) STATUS_CHOICES = ( ('A', 'Active'), ('C', 'Cancelled'), ) status = models.CharField(max_length=11, choices=STATUS_CHOICES) amount = models.PositiveIntegerField() item = models.ForeignKey(Item) ... </code></pre> <p>I want to write a query in my views.py to get the following for each Item:</p> <ol> <li>The total of the current (active) offers for this item</li> <li>The percentage of the target that has been met by offers for this item (i.e. [the total from (1)]/target_amount * 100)</li> </ol> <p>I have been trying to achieve this with "extra" as follows (using postgres):</p> <pre><code>items = Item.objects.filter(status='A').extra( select={ 'total_amount' : 'select coalesce(sum(amount),0) from myapp_offer where myapp_offer.item_id = myapp_item.id and myapp_offer.status = \'A\'', 'percentage_met' : '(((select coalesce(sum(amount),0) from myapp_offer where myapp_offer.item_id = myapp_item.id and myapp_offer.status = \'A\') / target_amount) * 100)' } ) </code></pre> <p>Now the first select (<code>total_amount</code>) is working correctly and returns what I expect, but the <code>percentage_met</code> is always 0. Can anyone help me out as to why?</p> <p>Edit: Should have mentioned that I want to be able to order_by the percentage_met</p>
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