Django查询与order

本文介绍了Django查询与order_by，distinct和限制在Postgresql的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我有以下内容：

class Product(models.Model): name = models.CharField(max_length=255) class Action(models.Model): product = models.ForeignKey(Product) created_at = models.DateTimeField(auto_now_add=True)

我想检索由created_at DESC订购的10个最新动作，包含不同的产品。

I would like to retrieve the 10 most recent actions ordered by created_at DESC with distinct products.

以下是接近结果但仍然错过了排序：

The following is close to the result but still misses the ordering:

Action.objects.all().order_by('product_id').distinct('product_id')[:10]

推荐答案

您的解决方案似乎正在尝试做太多事情。它还将导致2个单独的SQL查询。这可以正常工作，只需一个查询：

Your solution seems like it's trying to do too much. It will also result in 2 separate SQL queries. This would work fine and with only a single query:

action_ids = Action.objects.order_by('product_id', '-created_at')\ .distinct('product_id').values_list('id', flat=True) result = Action.objects.filter(id__in=action_ids)\ .order_by('-created_at')[:10]