Re: group by 3 fields

On Monday, February 27, 2017 at 3:52:38 AM UTC+1, Larry....@gmail.com wrote:

[SQL] That is a language I
have worked in for over 20 years, and when I see a querying need that
is how I think, and then I see how can I do that with the ORM. 

So I shouldn't give advices for you. We have similar experience, I think.

With Django you may play with .aggregate() and .annotate() functions.

You should be able to do grouping you need Just tell a ORM about aggregates you want to use, and it will automagically add group by. 

Let's try group by col1, col2:

> from django.db.models import Count

> from django.contrib.auth.models import User

> print User.objects.values('is_staff', 'is_superuser').annotate(cnt=Count('*')).query

SELECT `auth_user`.`is_staff`, `auth_user`.`is_superuser`, COUNT(*) AS `cnt` FROM `auth_user` GROUP BY `auth_user`.`is_staff`, `auth_user`.`is_superuser` ORDER BY NULL

You must tell Django that you need some aggregate, and then ask for selecting other values explicitely. These columns will be added to a group by.

Please note that as a result you will get iterable of dicts instead of model instances, which is pretty reasonable.

BR,

Marcin

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