Django Raw Annotations. I wanted to add some complex aggregates, but .extra(select=) adds your raw SQL to GROUP BY, which doesn't work for aggregates. So, I trick the annotate() function by creating my own class that pretends to be an aggregate, but really just dumps SQL. Do not use for user inputted data.

beautiful.sql

SELECT "businesses_business"."id", "businesses_business"."user_id", "businesses_business"."slug", "businesses_business"."name", "businesses_business"."business_type_id", "businesses_business"."street", "businesses_business"."additional", "businesses_business"."town", "businesses_business"."county", "businesses_business"."postcode_id", "businesses_business"."phone_number", "businesses_business"."fax_number", "businesses_business"."email", "businesses_business"."website", "businesses_business"."strapline", "businesses_business"."description", "businesses_business"."active", "businesses_business"."deleted", "businesses_business"."activation_code", "businesses_business"."created_on", "businesses_business"."account_confirmed", "businesses_business"."preview", "businesses_business"."paid", "businesses_business"."last_updated", "businesses_business"."copy_id", "businesses_business"."logo", "businesses_business"."security_reference", "businesses_business"."video", "businesses_business"."embed_url", "businesses_business"."premium", "businesses_business"."auto_resave_code", "businesses_business"."created_during_funeral_announcement", "businesses_business"."geocode_cache", "businesses_business"."charity_no", "businesses_business"."bank_name", "businesses_business"."bank_account_no", "businesses_business"."bank_sort_code",
   SUM("donation_donationamount"."amount") * 0.034 AS "total_charges",
   SUM("donation_payment"."amount") AS "total_payment",
   0.2 * COUNT("donation_donationamount"."amount") AS "total_20p",
   SUM("donation_donationamount"."amount") - (SUM("donation_donationamount"."amount") * 0.034 + 0.2 * COUNT("donation_donationamount"."amount")) AS "total_net",
   (SUM("donation_donationamount"."amount") - (SUM("donation_donationamount"."amount") * 0.034 + 0.2 * COUNT("donation_donationamount"."amount"))) - SUM("donation_payment"."amount") AS "total_balance",
SUM("donation_donationamount"."amount") AS "total_donation"
FROM "businesses_business"
INNER JOIN "businesses_businesstype" ON ("businesses_business"."business_type_id" = "businesses_businesstype"."id")
LEFT OUTER JOIN "donation_donationamount" ON ("businesses_business"."id" = "donation_donationamount"."business_id")
LEFT OUTER JOIN "donation_payment" ON ("businesses_business"."id" = "donation_payment"."business_id")
WHERE ("businesses_businesstype"."name" = Charity
       AND "donation_donationamount"."id" IS NOT NULL)
GROUP BY "businesses_business"."id",
         "businesses_business"."user_id",
         "businesses_business"."slug",
         "businesses_business"."name",
         "businesses_business"."business_type_id",
         "businesses_business"."street",
         "businesses_business"."additional",
         "businesses_business"."town",
         "businesses_business"."county",
         "businesses_business"."postcode_id",
         "businesses_business"."phone_number",
         "businesses_business"."fax_number",
         "businesses_business"."email",
         "businesses_business"."website",
         "businesses_business"."strapline",
         "businesses_business"."description",
         "businesses_business"."active",
         "businesses_business"."deleted",
         "businesses_business"."activation_code",
         "businesses_business"."created_on",
         "businesses_business"."account_confirmed",
         "businesses_business"."preview",
         "businesses_business"."paid",
         "businesses_business"."last_updated",
         "businesses_business"."copy_id",
         "businesses_business"."logo",
         "businesses_business"."security_reference",
         "businesses_business"."video",
         "businesses_business"."embed_url",
         "businesses_business"."premium",
         "businesses_business"."auto_resave_code",
         "businesses_business"."created_during_funeral_announcement",
         "businesses_business"."geocode_cache",
         "businesses_business"."charity_no",
         "businesses_business"."bank_name",
         "businesses_business"."bank_account_no",
         "businesses_business"."bank_sort_code"

example.py

from myapp.models import RawAnnotation

def get_charities(data=None):
    data = data or {}
    totals = {}
    charities = []
    
    # Bits of SQL
    total_donations = 'SUM("donation_donationamount"."amount")'
    total_charges = '{} * 0.034'.format(total_donations)
    total_20p = '0.2 * COUNT("donation_donationamount"."amount")'
    total_net = '{} - ({} + {})'.format(total_donations, total_charges, total_20p)
    total_payment = 'SUM("donation_payment"."amount")'
    total_balance = '({}) - {}'.format(total_net, total_payment)

    charities = (
        Business.objects
        .filter(business_type__name='Charity')
        .filter(donationamount__isnull=False)
        .annotate(
            total_donation=Sum('donationamount__amount'),
            total_payment=Sum('payment__amount'),
            total_charges=RawAnnotation(total_charges),
            total_20p=RawAnnotation(total_20p),
            total_net=RawAnnotation(total_net),
            total_balance=RawAnnotation(total_balance),
        )
    )

models.py

class RawAnnotation(object):
    # Needs to be an existing field. Doesn't matter which.
    lookup = 'pk'

    def __init__(self, extra):
        self.extra = extra

    def add_to_query(self, query, alias, col, source, is_summary):
        class FakeField(object):
            def get_internal_type(self):
                return None
        class FakeQuery(object):
            is_ordinal = False
            field = FakeField()
            is_computed = False
            def __init__(self, sql):
                self.sql = sql
            def as_sql(self, *args):
                return self.sql
        query.aggregates[alias] = FakeQuery(self.extra)

please help me:
i use thank hack for create raw annotate but i catch exception ValueError: too many values to unpack
why this exception raise?

lte = 'COALESCE("finance_actitem"."total"/ NULLIF("finance_act"."total"-"finance_act"."discount", 0), 0)'  
items = ActItem.objects.filter(
     Q(act__user=user.id) 
).annotate(
     lt=RawAnnotation(lte)
 ).filter(total__lte=F('lt'))