Django QuerySet首先在组中 [英] Django QuerySet First in Group

问题描述

我有一个查询集，看起来像：

  {id，group_id，date} 
  

对于由 group_id 键入的每个组，我想返回 id 与最早的日期。我如何在django查询中这样做？或者是更有效的order_by日期，然后使用python dict来忽略第一个相同group_id的所有元素？

解决方案

Django并没有真正拥有 GROUP BY 运算符。您可以尝试通过订购和 distinct（）来模拟它。

尝试这样的东西：

  queryset.order_by（'group_id'，'date'）。distinct（'group_id'）
 注意： group_id 必须先在订单中执行<$ c $（$）
 
 
 c> distinct（）操作。
 
I have a queryset that looks like:
{id, group_id, date}
For each group, keyed by the group_id, I'd like to return the id with the earliest date. How would I do that in a django query? Or is it more efficient to order_by date and then use a python dict to ignore all elements with the same group_id after the first?
解决方案
Django doesn't really have the GROUP BY operator.  You could try to mimic it with ordering and distinct().

Try something like this:
queryset.order_by('group_id', 'date').distinct('group_id')
Note: that the group_id has to be first in the ordering to perform the distinct() operation.

                        
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