Apologies. The code I posted is actually correct and well functioning.
The reason that the results looked wrong was that the data handled by the
code was faulty.
In my research, I found another way to do the trick:
contracts = (Project.objects.values('stage')
.annotate(contract_sum=Sum('contractSum'))
.annotate(expected_own_production_sum=Sum(
'id', field='contractSum * probability'))
)
cheers, Mikkel
lørdag den 4. august 2018 kl. 14.11.27 UTC+2 skrev Mikkel Kromann:
>
> Dear Django users.
>
> I'm trying to do the sums of the product of two columns ('contract_sum'
> and 'probability', decimal fields), grouping by a third column, 'stage' (a
> choice variable).
> I'm also reporting the grouped sums of one of the single columns
> ('contract_sum')
> The single column works just fine, but I just can't get it right with the
> product columns.
> Below is my code so far:
>
> contracts = (Project.objects.values('stage')
> .annotate(contract_sum=Sum('contractSum'))
> .annotate(expected_own_production_sum=F(
> 'contractSum')*F('probability'))
> )
>
> a) When I run the query with the single column query, the results are
> right.
> b) When I run the query with both selections, not only is the column
> product, wrong, but the single column sums also become wrong.
> c) When I run the query with only the product columns, the query returns
> zero for all groups, which is definitely wrong.
>
> Can I do this right without going to raw sql?
>
>
> cheers + thanks, Mikkel
>
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