Annotate QuerySet using raw SQL - django

Question

In case I am asking the wrong question, let me first state the end goal: I need to allow users to filter a ListView by a field that's not in the primary model (Salesleadquote), but instead the field comes from a model (Salesleadbusinessgroup) with a FK to a related model (Saleslead).
The way I am trying to approach this is by annotating a field on Salesleadquote.
The models:
class Salesleadquote(models.Model):
salesleadquoteid = models.AutoField(db_column='SalesLeadQuoteId', primary_key=True)
salesleadid = models.ForeignKey(Saleslead, models.DO_NOTHING, db_column='SalesLeadId')
...
class Saleslead(models.Model):
salesleadid = models.AutoField(db_column='SalesLeadId', primary_key=True)
...
class Salesleadbusinessgroup(models.Model):
salesleadbusinessgroupid = models.AutoField(db_column='SalesLeadBusinessGroupId', primary_key=True)
salesleadid = models.ForeignKey(Saleslead, models.DO_NOTHING, db_column='SalesLeadId')
businessgroupid = models.ForeignKey(Businessgroup, models.DO_NOTHING, db_column='BusinessGroupId')
The desired result (queryset), in SQL:
SELECT slq.*, slbg.BusinessGroupId FROM crm.SalesLeadQuote slq
LEFT JOIN
(SELECT SalesLeadId, BusinessGroupId
FROM crm.SalesLeadBusinessGroup ) slbg
ON slbg.SalesLeadId = slq.SalesLeadId
WHERE slbg.BusinessGroupId IN (5,21)
I know I can get a RawQuerySet by doing something like
Salesleadquote.objects.raw("SELECT salesleadquote.*, \
salesleadbusinessgroup.businessgroupid \
FROM salesleadquote \
LEFT JOIN salesleadbusinessgroup \
ON salesleadquote.salesleadid = salesleadbusinessgroup.salesleadid \
WHERE salesleadbusinessgroup.businessgroupid IN (5,21)")
But I need the functionality of a QuerySet, so my idea was to annotate the desired field (businessgroupid) in Salesleadquote, but I've been struggling with how to accomplish this.

Answer 1

I implemented a work-around that doesn't address my original question but works for my use case. I created a view at the database level (called SalesLeadQuoteBG) using the SQL I had posted and then tied that to a model to use with Django's ORM.
class Salesleadquotebg(models.Model):
"""
This model represents a database view that extends the Salesleadquote table with a business group id column.
There can be multiple business groups per quote, resulting in duplicate quotes, but this is handled at the view and template layer
via filtering (users are required to select a business group).
"""
salesleadquoteid = models.IntegerField(db_column='SalesLeadQuoteId', primary_key=True) # Field name made lowercase.
salesleadid = models.ForeignKey(Saleslead, models.DO_NOTHING, db_column='SalesLeadId') # Field name made lowercase.
...
businessgroupid = models.ForeignKey(Businessgroup, models.DO_NOTHING, db_column='BusinessGroupId')
I am using django-filters for the filtering.
filters.py:
BG_CHOICES = (
(5, 'Machine Vision'),
(21, 'Process Systems'),
)
class BGFilter(django_filters.FilterSet):
businessgroupid = django_filters.ChoiceFilter(choices=BG_CHOICES)
class Meta:
model = Salesleadquotebg
fields = ['businessgroupid', ]

Answer 2

This can be done with pure Django ORM. Relationships can be followed backwards (filtering on salesleadbusinessgroup) and the double underscore syntax can be used to query attributes of the related model and also follow more relationships
Salesleadquote.objects.filter(
salesleadbusinessgroup__businessgroupid__in=(5,21)
)