django数了一个字段但又被另一个字段分组

Question

So I am using django with mysql, and I have a model MyModel , which contains some items with None on the region field. When I run this:

results = MyModel.objects.all()\
        .values('region')\
        .annotate(total=Count('region'))

it returns the grouping correctly, but one is {'None': 0} , which is incorrect, because there are some items with region field equal to None .

Now, if I were using mysql then I could group this with:

select region, count(id) from model_table group by region;

which returns the solution I want | NULL | 5 | | NULL | 5 | .

How can I achieve this from django?

Answer 1

You actually already wrote the answer in your question. As far as I know, COUNT in SQL excludes certain falsey values like NULL. So if you want to count the falsey values as well, you use another field to perform the aggregate, just like you did in your SQL statement where you used the 'id' field. On that note, all you need to do is to perform COUNT on 'id'. Change your code to something like this:

results = MyModel.objects.all()\
    .values('region')\
    .annotate(total=Count('id'))