python Django-将SQL查询转换为ORM查询

Question

I want sql query to orm

SELECT id, title,
(SELECT SUM(AMOUNT) FROM web_history A WHERE A.car_id = B.id AND type = 3)
FROM web_car B;


histories = History.objects.filter(car=OuterRef('pk'), type=3)
cars = Car.objects.annotate(count=Subquery(histories.annotate(a=Sum('amount'))))

This can not be done by setting the output_field ... I can not solve it even if I apply variously from FloatField to Char through Concat. I leave a comment on whether I can get advice.

Answer 1

You seem to be overcomplicating things. You just need a query on Car which annotates the related Histories where type=3.

Car.objects.filter(history__type=3).annotate(count=Sum('history__amount'))