id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
28293	QuerySet.union(QuerySet.none()) results in an empty queryset, should be the original queryset	Jon Dufresne	Mariusz Felisiak	"Tested on Django 1.11.2.

As `QuerySet.union()` uses the SQL `UNION` operator, I would expect ""SET1 UNION <EMPTY SET>"" to result in SET1. Currently it results in the empty set.

{{{
>>> from django.contrib.auth.models import User
>>> User.objects.count()
100
>>> list(User.objects.all().union(User.objects.none()))
[]
}}}

From https://www.postgresql.org/docs/current/static/queries-union.html

> UNION effectively appends the result of query2 to the result of query1 ...

`QuerySet.difference()` looks to suffer from the same issue."	Bug	closed	Database layer (models, ORM)	1.11	Release blocker	fixed			Accepted	1	0	0	0	0	0