Django注释总和 [英] Django Annotate Sum

问题描述

我正在尝试为查询集中具有几行的一列获取一个简单的总和。我的直接问题是（a）如何设置 get_queryset（）包括列的总和，以及（b）如何访问模板中的该元素？遵循此问题：

I'm trying to get a simple sum for a column with several rows in a queryset. My direct question is (a) how do I set get_queryset() to include a sum of a column and (b) how do I access that element in a template? Following this question:

#models.py
class ItemPrice( models.Model ):
    price = models.DecimalField ( max_digits = 8, decimal_places=2 )
    ....

有两个答案-一个使用我不相信会返回查询集的 .aggregate（）方法和我所使用的 .annotate（）方法相信会将一个项目添加到查询集。

There are two answers provided - one using the .aggregate() method which I don't believe returns a queryset and .annotate() method which I believe appends an item to the queryset.

因此，我希望以下内容在该视图中将另一个项目添加到对象列表：

So, I would have expected that the following would add another item to the object list in this view:

#views.py
def get_queryset(self):
    # generate table and filter down to a subquery.
    queryset = ItemPrice.objects.filter(<some_filter>)
    # sum the price for each row in the subquery.
    queryset = queryset.annotate(totals=Sum('price'))
    return queryset

然后在模板中，我可以像这样遍历对象列表：

Then in the the Template, I would be able to iterate through the object list like this:

#template.html
{% for item in object_list %}
    {{ item }}
{% endfor %}

期望其中一项（最后一项？）将是 price_sum ，余额可以作为 price_sum.price 。

With the expectation that one of the items (the last item?) would be price_sum and that the balance could be accessed as price_sum.price.

但是，当我在模板中添加以下内容时，我会获得每个订单项的价格-没有总结。

However, when i add the following to my template, I get the prices for each line item - no summation.

{% for item in object_list %}
    {{ item.totals }}
{% endfor %}

但是，我无法访问该项目。我不知道问题是 get_queryset（）的视图修改还是在模板中？

But, I can't access the item. I don't know if the problem is the view modification of the get_queryset() or if it's in the template?

推荐答案

如果要将数据添加到模板

if you want to add data to the template

queryset = ItemPrice.objects.filter(<your_filter>)
totals = queryset.aggregate(sum=Sum('price').get('sum')

context  = {
    'object_list': queryset,
    'totals': totals,
}
render(request, '<name_of_your_template>.html', context)

并在您的模板中

{% for item in object_list %}
    # price of item
    {{ item.price }}
{% endfor %}
# total price
{{ totals }}

这篇关于Django注释总和的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！