Django subquery using QuerySet

Question

Is it possible to perform a subquery on a QuerySet using another QuerySet?

For example:

q = Something.objects.filter(x=y).extra(where=query_set2)

What are you really trying to do here? The code makes no sense to me. Do you really want to do query_set2.filter(something__x=y)? — Deniz Dogan
– Deniz Dogan, Commented Sep 22, 2010 at 13:02

Manoj Govindan · Accepted Answer · 2010-09-22 13:03:23Z

6

Short answer: No. The extra method doesn't expect querysets to be passed in.

If you think about it a bit, it makes sense. Querysets are an abstraction used to represent the results of a fetch operation on the database and extra is a convenient way of attaching custom fields from the database to a queryset. Unless you change the fundamental nature of extra to mean "custom filtering with another queryset" this will not work.

edited Sep 22, 2010 at 13:03

answered Sep 22, 2010 at 12:55

Manoj Govindan

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Soravux · Accepted Answer · 2010-09-22 15:21:32Z

2

I may understand your question in two ways.

You can specify multiple variables in your filter parameters, for example :
```
q = Something.objects.filter(x=y, w=z)
```
You want to make what is called a "join" in SQL. This can be done via the aggregation system of Django, see the official Django Official Documentation.

answered Sep 22, 2010 at 15:21

Soravux

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