How to do SELECT MAX in Django?

Question

See this. Your code would be something like the following:

from django.db.models import Max
# Generates a "SELECT MAX..." query
Argument.objects.aggregate(Max('rating')) # {'rating__max': 5}

You can also use this on existing querysets:

from django.db.models import Max
args = Argument.objects.filter(name="foo") # or whatever arbitrary queryset
args.aggregate(Max('rating')) # {'rating__max': 5}

If you need the model instance that contains this max value, then the code you posted is probably the best way to do it:

arg = args.order_by('-rating')[0]

Note that this will error if the queryset is empty, i.e. if no arguments match the query (because the [0] part will raise an IndexError). If you want to avoid that behavior and instead simply return None in that case, use .first():

arg = args.order_by('-rating').first() # may return None

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