DateTimeField queryset在Django中返回None [英] DateTimeField queryset returning None in Django

问题描述

我正在尝试创建一个查询器来获取数据库中DATETIME的DateTimeField的值。

I am trying to create a queryset for getting the values of a DateTimeField which is DATETIME in the DB.

model.py中的类：

The class in models.py:

class ChangeMetrics(models.Model):
    id = models.IntegerField(primary_key=True)
    file_id = models.ForeignKey(File, db_column = 'file_id')
    version_id = models.ForeignKey(Version, db_column = 'version_id')
    function_id = models.ForeignKey(Function, blank=True, db_column = 'function_id')
    date = models.DateTimeField(blank=True, null=True)
    user = models.TextField(blank=True)
    changed = models.IntegerField(blank=True, null=True)

DB中的字段：

date DATETIME

数据库中填充了元组，直接在数据库上运行SQL查询正常工作。

The tuples are populated in the database and running SQL queries directly on the DB is working perfectly.

这是我目前在Django中使用的查询器：

This is the queryset I am currently using in Django:

queryset = ChangeMetrics.objects.filter(~Q(changed=None), ~Q(date=None), ~Q(version_id=None))

我尝试过一个原始查询，还有一个使用exclude（）的查询版本，但仍然返回None。

I have tried a raw query and also a version of the query that uses exclude(), but that still returns None for date.

我正在通过for循环访问查询集中的条目，只需通过for循环中的entry.date访问日期。

I am accessing the entries in the queryset through a for loop and simply accessing date through entry.date inside the for loop.

编辑：
Django版本1.6.5
我也尝试通过Django shell获取值，没有成功。

Django version 1.6.5 I have also tried getting the values through the Django shell, to no success.

任何想法可能是错的？

推荐答案

不确定如果你能够弄清楚这一点，但我刚刚遇到这个问题，并能够解决它。

not sure if you were able to figure this out, but I just had this problem and was able to fix it.

所以，Django迁移在数据库中创建列为datetime（6）而不是datetime。这导致Django模型无法实例化日期时间对象。

So, Django migrations were creating the column in the DB as datetime(6) instead of datetime. This was causing the Django models to fail to instantiate the Datetime object.

ALTER TABLE `my_table` 
MODIFY COLUMN `created` datetime NOT NULL

运行后如果修正了我的问题。也许在您的情况下，您可以尝试修改为datetime（6）。

After running that if fixed my issue. Maybe in your case you could try modifying to datetime(6) instead.

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