I have a model with datetime field which is the time stamp of when the row was added and in this model/table continuous entries are being made at certain intervals from various sources which are referenced through a name which is also a field in the model.
我有一个带有日期时间字段的模型，该字段是添加行的时间戳，在此模型/表格中，连续条目是从各种来源以特定间隔进行的，这些来源通过名称引用，该名称也是模型中的字段。
I need to form a query so that I will fetch the row with latest datetime when grouped by name.
我需要形成一个查询，以便在按名称分组时获取最新日期时间的行。
i.e. lets say for example table is something like this:
也就是说，例如表格是这样的：
timestamp entry_name
22 march 12:30 First
22 march 12:32 Second
22 march 12:42 First
22 march 12:50 Second
My query should result in:
我的查询应该导致：
22 march 12:42 First
22 march 12:50 Second
As they are the latest entries with respect to "First" and "Second" group.
因为它们是关于“第一”和“第二”组的最新条目。
Now using raw query its pretty straight forward:
现在使用原始查询非常直接：
select *,max(datetime) from entry_table GROUP BY entry_name;
Is there any simple way to do this through the ORM?
有没有简单的方法通过ORM做到这一点？
Thanks in advance!
提前致谢！
1 个解决方案
#1
1
I use this in my own projects. The order_by and values make it group by name
我在自己的项目中使用它。 order_by和values使其按名称分组
from django.db import models
Model.objects.order_by('name').values('name').annotate(max_timestamp=models.Max("timestamp"))
#1
1
I use this in my own projects. The order_by and values make it group by name
我在自己的项目中使用它。 order_by和values使其按名称分组
from django.db import models
Model.objects.order_by('name').values('name').annotate(max_timestamp=models.Max("timestamp"))