title: How can i implement coalesce query in django?
body: <p>I'm trying to build an ecom website using django and djngo rest framework. My model Item contains price and sale_price column:</p>
  <pre><code>class Item(models.Model):
      price = models.FloatField()
      sale_price = models.FloatField(null=True,blank=True)
  </code></pre>
  <p>I want to filter them by max active price
  So in order to do that in sqlite i would write something like</p>
  <pre><code>SELECT * FROM item WHERE coalesce(sale_price,price) &lt; maxPrice;
  </code></pre>
  <p>How can i do this in Django?</p>