Python 在 Django 中与众不同

DISTINCT ON in django

提问by David542

How would I do the following query:

我将如何执行以下查询：

OrderNotes.objects.filter(item=item).distinct('shared_note')

Basically, I need to get all OrderNotesitems, distinct on shared_note. When I try and do this I get:

基本上，我需要获取所有OrderNotes项目，在shared_note. 当我尝试这样做时，我得到：

    raise NotImplementedError('DISTINCT ON fields is not supported by this database backend')

NotImplementedError: DISTINCT ON fields is not supported by this database backend

I am using mysql and cannot change the db here. What would be the workaround in django?

我正在使用 mysql 并且无法在此处更改数据库。Django 中的解决方法是什么？

采纳答案by catherine

OrderNotes.objects.filter(item=item).values_list('shared_note', flat=True).distinct()

回答by David542

This is the best I came up with:

这是我想出的最好的：

>>> items, item_ids = [], []
>>> for item in OrderNotes.objects.filter(shared_note=219):
...     if item.shared_note not in item_ids:
...         items.append(item)
...         item_ids.append(item.shared_note)