django-orm - 我可以从 Django ORM 查询中删除 ORDER BY 吗？

Question

似乎 Django 默认会添加ORDER BY到查询中。我可以清除它吗？

from slowstagram.models import InstagramMedia
print InstagramMedia.objects.filter().query

SELECT
  `slowstagram_instagrammedia`.`id`,
  `slowstagram_instagrammedia`.`user_id`, 
  `slowstagram_instagrammedia`.`image_url`,
  `slowstagram_instagrammedia`.`video_url`,  
  `slowstagram_instagrammedia`.`created_time`,  
  `slowstagram_instagrammedia`.`caption`, 
  `slowstagram_instagrammedia`.`filter`, 
  `slowstagram_instagrammedia`.`link`, 
  `slowstagram_instagrammedia`.`attribution_id`, 
  `slowstagram_instagrammedia`.`likes_count`, 
  `slowstagram_instagrammedia`.`type`
FROM
  `slowstagram_instagrammedia`
ORDER BY
  `slowstagram_instagrammedia`.`id`
ASC

```

Answer 1

其实，做一个query.order_by()就够了。

这是在文档中指定的，虽然有点难找。文档说：

如果您不希望将任何排序应用于查询，即使是默认排序也不行，请不带参数调用 order_by()。

下面是实现order_by，供大家参考——

def order_by(self, *field_names):
    """
    Returns a new QuerySet instance with the ordering changed.
    """
    assert self.query.can_filter(), \
        "Cannot reorder a query once a slice has been taken."
    obj = self._clone()
    obj.query.clear_ordering(force_empty=False)
    obj.query.add_ordering(*field_names)
    return obj

Answer 2

您可以使用：clear_ordering来自查询的方法

"""Removes any ordering settings. 

If 'force_empty' is True, there will be no ordering in the resulting
query (not even the model's default).
"""

例子：

>>> from products.models import Product
>>> products = Product.objects.filter(shortdesc='falda').order_by('id')
>>> print products.query
SELECT "products_product"."id", "products_product"."shortdesc"
WHERE "products_product"."shortdesc" = falda
ORDER BY "products_product"."id" ASC
>>> products.query.clear_ordering()
>>> print products.query
SELECT "products_product"."id", "products_product"."shortdesc"
WHERE "products_product"."shortdesc" = falda

Answer 3

尝试.order_by('?')在查询集末尾使用。