问题描述

最近开始使用Django ORM.我想执行这个查询

 select student_id from student_id like "%97318%" order by CAST(student_id as UNSIGNED) desc;
其中 student_id 是一个 CharField，我希望将其作为整数进行查询.我试过
 student.objects.filter(student_id__contains "97318").order('-student_id')
工作正常.但是不知道也找不到如何将student_id"转换为 int 就像上面提到的Django ORM"的实际 MySQL 查询一样.我应该使用原始查询还是有出路?让我知道您的建议.
 解决方案 
无需使用 extra 的更新替代方案是 cast 函数(Django 1.10 中的新功能):
<预><代码>>>>从 django.db.models 导入 FloatField>>>从 django.db.models.functions 导入 Cast>>>Value.objects.create(整数=4)>>>value = Value.objects.annotate(as_float=Cast('integer', FloatField())).get()>>>>打印(value.as_float)4.0

来自 https://docs.djangoproject.com/en/1.10/ref/models/database-functions/#cast

Recently started using Django ORM.I want to execute this query

 select student_id from students where student_id like "%97318%" order by CAST(student_id as UNSIGNED) desc;   

where student_id is a CharField which I want as integer for querying. I tried with

  students.objects.filter(student_id__contains "97318").order('-student_id')

works fine. But don't know and couldn't find how to cast "student_id" to int like the actual MySQL query mentioned above with "Django ORM". should I use raw query or is there a way out? Let me know your suggestions.

An updated alternative without requiring the use of extra is the cast function (new in Django 1.10):

>>> from django.db.models import FloatField
>>> from django.db.models.functions import Cast
>>> Value.objects.create(integer=4)
>>> value = Value.objects.annotate(as_float=Cast('integer', FloatField())).get()> 
>>> print(value.as_float)
4.0

From https://docs.djangoproject.com/en/1.10/ref/models/database-functions/#cast

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