Django Query month wise with last 6 month - django

Question

I am trying to query and the group is the Order of the last 6 months.
and this is my models:
class Order(models.Model):
created_on = models.DateTimeField(_("Created On"), auto_now_add=True)
and this is my method to parse month:
from django.db.models import Func
class Month(Func):
"""
Method to extract month
"""
function = 'EXTRACT'
template = '%(function)s(MONTH from %(expressions)s)'
output_field = models.IntegerField()
And this is my query:
current_date = date.today()
months_ago = 6
six_month_previous_date = current_date - timedelta(days=(months_ago * 365 / 12))
order = Order.objects.filter(
created_on__gte=six_month_previous_date,
).annotate(
month=Month('created_on')
).values(
'month'
).annotate(
count=Count('id')
).values(
'month',
'count'
).order_by(
'month'
)
In my database order table, there is only on entry:
So it is returning
[{'month': 10, 'count': 1}]
But i dont want like this, i want like these of last 6 month, if in one month, there is no sales, it should return the count: 0
Like thise bellow:
[
{'month': 10, 'count': 1},
{'month': 9, 'count': 0}
{'month': 8, 'count': 0}
{'month': 7, 'count': 0}
{'month': 6, 'count': 0}
{'month': 5, 'count': 0}
]

Answer 1

A database works under the closed world assumption, so it will not insert rows with 0. You can however post-process the list.
from django.utils.timezone import now
order = Order.objects.filter(
created_on__gte=six_month_previous_date,
).values(
month=Month('created_on')
).annotate(
count=Count('id')
).order_by('month')
order = {r['month']: r['count'] for r in order}
month = now().month
result = [
{'month': (m % 12)+1, 'count': order.get((m % 12) + 1, 0)}
for m in range(month-1, month-8, -1)
]
Note that Django already has an ExtractMonth function [Django-doc].