model.py
class Tdzien(models.Model):
dziens = models.SmallIntegerField(primary_key=True, db_column='DZIENS')
dzienrok = models.SmallIntegerField(unique=True, db_column='ROK')
class Tnogahist(models.Model):
id_noga = models.ForeignKey(Tenerg, primary_key=True, db_column='ID_ENERG')
dziens = models.SmallIntegerField(db_column='DZIENS')
What I want is to get id_noga where dzienrok=1234. I know that dziens should be
dziens = models.ForeignKey(Tdzien)
but it isn't and I can't change that. Normally I would use something like
Tnogahist.objects.filter(dziens__dzienrok=1234)
but I don't know how to join and filter those tables without foreignkey.
It's possible to join two tables by performing a raw sql query. But for this case it's quite nasty, so I recommend you to rewrite your models.py.
You can check how to do this here
It would be something like this:
from django.db import connection
def my_custom_sql(self):
cursor = connection.cursor()
cursor.execute("select id_noga
from myapp_Tnogahist a
inner join myapp_Tdzien b on a.dziens=b.dziens
where b.dzienrok = 1234")
row = cursor.fetchone()
return row
No joins without a foreign key as far as I know, but you could use two queries:
Tnogahist.objects.filter(dziens__in=Tdzien.objects.filter(dzienrok=1234))
Could you do this with .extra? From https://docs.djangoproject.com/en/dev/ref/models/querysets/#extra:
where / tables
You can define explicit SQL WHERE clauses — perhaps to perform
non-explicit joins — by using where. You can manually add tables to
the SQL FROM clause by using tables.
