CODEWITHSUNDEEP
django
sean2000
sean2000

Reputation: 516

Django query equivalent of MySQL GREATEST function?

How can i get the greater of two different Decimal fields for a model using a Django query?

For example if i have a model Month with fields called income_actual and income_projected, how do i return the greater value?

I have previously used the MySQL GREATEST() function to do it but i cant work out how to do it in Django.

Upvotes: 3

Views: 1090

Answers (3)

Chirag Maheshwari
Chirag Maheshwari

Reputation: 421

You may use Django's Database Function Greatest.

For example you may use such a query:

>>> from django.db.models.functions import Greatest

>>> months = Month.objects.annotate(greatest_income=Greatest('income_actual', 'income_projected').all()

# now you can access the greatest value using something like this:
>>> months[0].greatest_income

Upvotes: 2

user234932
user234932

Reputation:

@drewman already gave you the version when you want to use strictly SQL. I would do things a bit differently, and add a property to the model which dynamically calculates the correct version.

class model(models.Model):
    ....

    @property
    def income(self):
        return max(self.income_actual, self.income_real)

Upvotes: 0

drewman
drewman

Reputation: 1595

Have you looked into using the extra method?

Month.objects.extra(select={'max_income': 'greatest(income_actual, income_projected)'})

EDIT:

You're not going to be able to use that through the ORM without writing raw SQL. Although you could use some python magic:

sum(month['max_income'] for month in Month.objects.extra(select={'max_income': 'greatest(income_actual, income_projected)'}).values('max_income'))

Upvotes: 3

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