django : How to write alias in queryset

Question

How can one write an alias for the column name in django query set. Would be useful for union-style combinations of two linked field to the same foreign model (for instance).

for example in mysql :

select m as n, b as a from xyz

how can i do this in django query set ?

models.Table.objects.all().values('m', 'b')

Any help really appreciate it.

Answer 1

Your reason in the comment makes no sense. Each field in the model has its own column in the database, and there's never any danger of mixing them up. You can of course tell a field to use a column name that's different from the field name:

myfield = models.CharField(max_length=10, db_column='differentname')

but I don't know if that will help you, because I still don't know what your problem is.

Answer 2

You can annotate the fields as you want, with the F expression:

from django.db.models import F

models.Table.objects.all().values('m', 'b').annotate(n=F('m'), a=F('b'))

Answer 3

Although this could have been done before by using extra(select={'n':'m','a':'b'}), I agree that this really should have been a part of values() itself.

To that end, and inspired by Alex's ticket, I have just posted a patch that adds this feature. I hope you'll find it useful!