python Django - Convert SQL Query to ORM Query

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.

Daniel Roseman · Accepted Answer · 2017-12-19 09:31:01Z

2

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'))

edited Dec 19, 2017 at 9:31

answered Dec 19, 2017 at 9:13

Daniel Roseman

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2 Comments

강준우 Over a year ago

Hm.. How do you access the History table? 'Type' and 'Amount' are the columns of History

Daniel Roseman Over a year ago

You use the double-underscore syntax, see my edit - I was already doing so for type, needed to add it for history as well.

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