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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