Django select distinct sum
- by yoshi
I have the following (greatly simplified) table structure:
Order:
order_number = CharField
order_invoice_number = CharField
order_invoice_value = CharField
An invoice number can be identical on more than one order (order O1 has invoice number I1, order O2 has invoice number I1, etc.). All the orders with the same invoice number have the same invoice value.
For example:
Order no. Invoice no. Value
O1 I1 200
O2 I1 200
O3 I1 200
04 I2 50
05 I2 100
What I am trying to do is do a sum over all the invoice values, but don't add the invoices with the same number more than once. The sum for the above items would be: 200+50+100.
I tried doing this using
s = orders.values('order_invoice_id').annotate(total=Sum('order_invoice_value')).order_by()
and
s = orders.values('order_invoice_id').order_by().annotate(total=Sum('order_invoice_value'))
but I didn't get the desired result. I tried a few different solutions from similar questions around here but I couldn't get the desired result.
I can't figure out what I'm doing wrong and what I actually should do to get a sum that uses each invoice value just once.
