how to add a condition of comparing two fields of the model itself in Django model query

Question

As mentioned by the title, in Django:

Say I have a model name QuestionRecord, with two fields: full_score and actual_score. I want to realize the SQL:

select * from QuestionRecord as QR where QR.full_score!=QR.actual_score.

Maybe using raw sql is OK, but I want to implement it like this:

class QuestionRecord_QuerySet(models.query.QuerySet):
    def incorrect(self):# Find out those whose full_score and actual_score are not equal
        return self.filter(...) # **What should I write here??**

class QuestionRecord_Manager(models.Manager):
    def get_query_set(self):
        return QuestionRecord_QuerySet(self.model)

class QuestionRecord(models.Model):
    objects = QuestionRecord_Manager()

Is there any way to do it?

Answer 1

Sure, that's what the "F" object is for!

from django.db.models import F

# snip

    return self.exclude(full_score = F('actual_score'))

---

Use QuerySet.exclude here, as you want to not get the results that match.

If you really want to use QuerySet.filter, you can use a negated "Q" object: self.filter(~Q(full_score = F('actual_score'))).