Join Multiple Querysets From Different Base Models Django

user_809839 0
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I currently have two different models.

class Journal(models.Model):
    date = models.DateField()
    from_account = models.ForeignKey(Account,related_name='transferred_from')
    to_account = models.ForeignKey(Account,related_name='transferred_to')
    amount = models.DecimalField(max_digits=8, decimal_places=2)
    memo = models.CharField(max_length=100,null=True,blank=True)

class Ledger(models.Model):
    date = models.DateField()
    bank_account = models.ForeignKey(EquityAccount,related_name='paid_from')
    account = models.ForeignKey(Account)
    amount = models.DecimalField(max_digits=8, decimal_places=2)
    name = models.ForeignKey(Party)
    memo = models.CharField(max_length=100,null=True,blank=True)

I am creating a report in a view and get the following error: Merging 'ValuesQuerySet' classes must involve the same values in each case.

What I'm trying to do is only pull out the fields that are common so I can concatenate both of them e.g. 

def report(request):

    ledger = GeneralLedger.objects.values('account').annotate(total=Sum('amount'))
    journal = Journal.objects.values('from_account').annotate(total=Sum('amount'))
    report = ledger & journal
...

If I try to make them exactly the same to test e.g.

def report(request):

    ledger = GeneralLedger.objects.values('memo').annotate(total=Sum('amount'))
    journal = Journal.objects.values('memo').annotate(total=Sum('amount'))
    report = ledger & journal
...

I get this error: Cannot combine queries on two different base models.

Anyone know how this can be accomplished?

concatenation django-queryset join django
3 Answers

Use itertools.chain:

from itertools import chain
report = list(chain(ledger, journal))

Note: you need to turn the resulting object into a list for Django to be able to process it.

user_101716950

I had the same issue. I solved it using the union method combined_queryset = qs1.union(qs2)

Using your example: report = ledger.union(journal)

user_106151380
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