python 3.x - Django Rest : AssertionError: Cannot combine a unique query with a non-unique query

Question

I am trying to get a queryset with unique instances of a model project. when I try to combine multiple querysets with & operator like

projects = (q1_projects & q2_projects & q3_projects)

I get this error

AssertionError: Cannot combine a unique query with a non-unique query.

question from:https://stackoverflow.com/questions/65916658/django-rest-assertionerror-cannot-combine-a-unique-query-with-a-non-unique-qu

Answer 1

As quoted by ruddra

You can use union() to combine different querysets like this:

q1_projects = Model.objects.filter(...)
q2_projects = Model.objects.filter(...)
q3_projects = Model.objects.filter(...)

projects = q1_projects.union(q2_projects, q3_projects)

That will give same result as:

projects = q1_projects & q2_projects & q3_projects

Note: The UNION operator selects only distinct values by default. To allow duplicate values, use the all=True argument.

But if you want to order_by on the ForeignKey, you have to use select()