如何在Django中选择不同的值? [英] How do I select distinct values in Django?

问题描述

这是我的代码:

[app.system_name for app in App.objects.all().distinct('system_name')]

给我:

[u'blog', u'files', u'calendar', u'tasks', u'statuses', u'wiki', u'wiki', u'blog
', u'files', u'blog', u'ideas', u'calendar', u'wiki', u'wiki', u'statuses', u'ta
sks', u'survey', u'blog']

您可能希望我想要system_name字段的所有唯一值，但是现在我只获取了所有App实例.

As you might expect I want all the unique values of the field system_name, but now I just get all App instances back.

推荐答案

1. 仅在Django 1.4及更高版本中支持在 distinct 中指定字段.如果您运行的是1.3，那就只是忽略它.

1. Specifying fields in distinct is only supported in Django 1.4+. If you're running 1.3, it's just ignoring it.

如果正在运行Django 1.4，则必须添加一个 order_by 子句，该子句包括并以 distinct 中的所有字段开头.

If you are running Django 1.4, you must add an order_by clause that includes and starts with all the fields in distinct.

即使这样，也仅在PostgreSQL上支持使用 distinct 指定字段.如果您正在运行其他内容(例如MySQL)，则说明您不走运.

Even then, specifying fields with distinct is only support on PostgreSQL. If you're running something else, such as MySQL, you're out of luck.

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