How to Cast a CharField to an Integer for Django ORM Querying?

Casting Char Field to Integer for Django ORM Querying

When querying a database using Django's Object-Relational Mapping (ORM), it may be necessary to cast a CharField to an integer for comparison or sorting purposes. This can be problematic as CharFields are stored as strings by default.

One approach to overcome this challenge is using the Django ORM's filter() method with the contains argument. However, this method only checks for string matches.

To achieve casting within the ORM, Django offers the Cast function, which can convert a field to a different data type. This function was introduced in Django version 1.10.

<code class="python">from django.db.models import FloatField
from django.db.models.functions import Cast

# Assuming 'student_id' is a CharField
students = Student.objects.annotate(
    converted_student_id=Cast('student_id', FloatField())
).filter(converted_student_id__contains="97318").order_by('-converted_student_id')</code>

In this updated approach, the Cast function transforms the student_id CharField to a FloatField, enabling comparison and sorting on the numerical value rather than the string value. This provides a more efficient and accurate way of querying your data.

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