如何在Django F表达式中将日期和时间字段合并为DateTime字段 [英] How to Combine Date and Time Fields into DateTime Field in Django F Expression

问题描述

我必须得到两个 datetime 字段的差额，但一个是纯datetime字段，另一个是日期和时间的组合。
我尝试了这个：

I have to get the difference of two datetime fields but one is pure datetime field and other is a combination of date and time. I tried this one:

    qs = Foo.objects.filter(
        bar__baz_id=self.kwargs['baz_pk'],
    )
    start_datetime = ExpressionWrapper((F('x__date') + F('x__start')), output_field=DateTimeField())
    qs = qs.annotate(start_datetime=start_datetime)
    before_start_wrapper = ExpressionWrapper(
        F('start') - F('start_datetime'),   # 'start' is datetime field on Foo, start_datetime is annotated field on Foo
        output_field=DateTimeField()
    )
    before_start = Extract(before_start_wrapper, 'epoch')
    qs = qs.annotate(before_start=before_start/3600)

这也不起作用；

    qs = Foo.objects.filter(
        bar__baz_id=self.kwargs['baz_pk'],
    )
    start_datetime = F('x__date') + F('x__start')

    before_start_wrapper = ExpressionWrapper(
        F('start') - F(start_datetime), # 'start' is datetime field on Foo, start_datetime is combined F expression
        output_field=DateTimeField()
    )
    before_start = Extract(before_start_wrapper, 'epoch')
    qs = qs.annotate(before_start=before_start/3600)

django的功能如下：

What django does is as follows:

...(EXTRACT('epoch' FROM "foo".came" - ("db_shift"."date" + "db_shift"."start")) AT TIME ZONE) /3600 AS ...

我期望的是：

...(EXTRACT('epoch' FROM "foo".came" - ("db_shift"."date" + "db_shift"."start")AT TIME ZONE)) / 3600 AS ...

请问有人可以提供解决方案吗？ Django ORM？我知道我可以运行原始查询，但是想看看是否有一种方法可以对Django ORM进行同样的操作？

Can some one please provide the solution with Django ORM? I know I can run a raw query but wanted to look if there is a way to do the same with Django ORM?

谢谢。

推荐答案

我已经解决了该问题并得到了答案。只需要 ExpressionWrapper 输出参数中的 DurationField（） c>而不是 DateTimeField（）。下面是代码：

I have worked around the issue and got the answer. Only need the DurationField() in the output param of the ExpressionWrapper instead of DateTimeField(). Here is the code:

qs = Foo.objects.filter(
    bar__baz_id=self.kwargs['baz_pk'],
)
start_datetime = F('x__date') + F('x__start')

before_start_wrapper = ExpressionWrapper(
    F('start') - F(start_datetime), # 'start' is datetime field on Foo, start_datetime is combined F expression
    output_field=DurationField()
)
before_start = Extract(before_start_wrapper, 'epoch')
qs = qs.annotate(before_start=before_start/3600)

通过这种方式我可以管理问题我早一点。这可能对其他人有帮助。

This way I got to manage the issue I had earlier. This might be helpful for someone else.

这篇关于如何在Django F表达式中将日期和时间字段合并为DateTime字段的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！