Django slice a single field in a queryset

问题:

I am trying to grab the first five characters from a char field but for only one field in a queryset but I keep getting various errors. Is there an effective way to do this in the view?

Code I am trying:

var = Model.objects.values('field1', 'field2'[:5], 'field3')

回答1:

You can annotate the queryset with first 5 letters of field2 using Substr function:

from django.db.models.functions import Substr  queryset = Model.objects.all()  queryset = queryset.annotate(field2_5=Substr('field2', 1, 5)) 

And, then use the annotated field field2_5 in values:

values = queryset.values('field1', 'field2_5', 'field3')

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