Django ORM IF statement - django

Question

I have this table
With SQL query i can get aggregated information about total "amount" for avery car, and amount of "checked"|"uncheked" rows and sign of finished checking for all rows for one car:
SELECT
car_id
, SUM(amount) as total_amount
, Sum(IF(checked=1,1,0)) as already_checked
, Sum(IF(checked=0,1,0)) as not_cjecked
, IF(Sum(IF(checked=0,1,0))=0,1,0) as check_finished
FROM
refuels_flow
GROUP BY car_id
Result:
+--------+--------------+-----------------+-------------+----------------+
| car_id | total_amount | already_checked | not_cjecked | check_finished |
+--------+--------------+-----------------+-------------+----------------+
| 1 | 1300 | 1 | 12 | 0 |
| 2 | 300 | 3 | 0 | 1 |
+--------+--------------+-----------------+-------------+----------------+
The question is - how i can do this with Django ORM (without use of raw query)?

Answer 1

To obtains the same SQL output, you may use the following queryset:
already_checked = Sum(Func('checked', function='IF', template='%(function)s(%(expressions)s=0, 0, 1)'))
not_checked = Sum(Func('checked', function='IF', template='%(function)s(%(expressions)s=0, 1, 0)'))
check_finished = Func(
not_checked,
function='IF', template='%(function)s(%(expressions)s=0, 1, 0)'
)
Refuels.objects.values('car_id').annotate(
total_amount=Sum('amount'),
already_checked=already_checked,
not_checked=not_checked,
check_finished=check_finished
)
Check the doc on expressions for more informations.
Now, already_checked could be simplified with:
already_checked = Sum('checked')
And instead of having the not_checked and check_finished annotations, you could annotate the count and easily compute them in Python, for example:
qs = Refuels.objects.values('car_id').annotate(
count_for_car=Count('car_id'),
total_amount=Sum('amount'),
already_checked=Sum('checked'),
)
for entry in qs:
not_checked = entry['count_for_car'] - entry['already_checked']
check_finished = not_checked == 0