How to Convert a CharField to an Integer in Django ORM Queries?

Casting Char to Integer in Django ORM Queries

In Django ORM, you may encounter scenarios where you need to convert a CharField to an integer for querying purposes. Let's explore the options available:

Original Query:

<code class="mysql">select student_id from students where student_id like "%97318%" order by CAST(student_id as UNSIGNED) desc;</code>

Standard Query:

<code class="python">students.objects.filter(student_id__contains="97318").order_by('-student_id')</code>

This query lacks the casting functionality of the MySQL query, resulting in a mismatch.

Using the Cast Function:

From Django 1.10 onward, the Cast function enables casting of fields to various data types. In this case, you can use:

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

students.objects.annotate(student_id_int=Cast('student_id', FloatField()))\
    .filter(student_id__contains="97318").order_by('-student_id_int')</code>

Raw Query:

As an alternative, you can utilize a raw query to achieve the casting:

<code class="python">from django.db import connection

cursor = connection.cursor()
cursor.execute("""
    SELECT student_id
    FROM students
    WHERE student_id LIKE '%%97318%%'
    ORDER BY CAST(student_id AS UNSIGNED) DESC
""")
student_ids = cursor.fetchall()</code>

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