How to use left join orm? - django

Question

My model
class Ad_company(models.Model):
idx = models.AutoField(primary_key=True)
subject = models.CharField(max_length=255)
memo = models.CharField(max_length=255)
content = models.TextField()
is_display = models.CharField(max_length=1)
writer = models.CharField(max_length=255)
write_date = models.DateTimeField()
update_date = models.DateTimeField()
delete_date = models.DateTimeField()
deadline_date = models.DateTimeField()
reply = models.IntegerField(blank=True)
hits = models.IntegerField(blank=True)
ad_apply = models.IntegerField(blank=True)
ad_category1 = models.CharField(max_length=255)
ad_category2 = models.CharField(max_length=255)
ad_place = models.CharField(max_length=255)
ad_age = models.CharField(max_length=255)
ad_sex = models.CharField(max_length=255)
ad_budget = models.BigIntegerField()
ad_length = models.CharField(max_length=255)
is_done = models.CharField(max_length=1)
is_pay = models.CharField(max_length=1)
ad_service = models.CharField(max_length=255)
ad_object = models.CharField(max_length=255)
is_file = models.CharField(max_length=1)
ad_require = models.CharField(max_length=255)
class Meta:
managed = False
db_table = 'ad_write_company'
class Ad_company_apply(models.Model):
idx = models.AutoField(primary_key=True)
parent_idx = models.IntegerField()
username = models.CharField(max_length=255)
content = models.TextField()
date = models.DateTimeField(default=datetime.now, blank=True)
budget = models.BigIntegerField()
term = models.IntegerField()
is_done = models.CharField(max_length=1)
SELECT * FROM ad_write_company INNER JOIN ad_write_company_apply ON ad_write_company.idx = ad_write_company_apply.parent_idx where ad_write_company_apply.is_done = 1 and ad_write_company_apply.username = 'asdffdsa'
This is my query. but I can not make join query with orm.
Sorry for question is too short.
And Is my query right?
I not sure of that. Thanks for answer.
or do you guys have other good idea?

Answer 1

I would advise to work with a ForeignKey from Ad_company_apply to Ad_company. This makes it easier to generate queries in Django and will guarantee referential integrity.
It thus makes sense to rewrite the Ad_company_apply model to:
class Ad_company_apply(models.Model):
# …
parent_idx = models.ForeignKey(
Ad_company,
db_column='parent_idx',
on_delete=models.CASCADE
)
# …
In that case, you can .filter(…) [Django-doc] with:
Ad_Company.objects.filter(ad_company_appy__isdone=1, ad_company_appy__username='asdffdsa')
Note: Models in Django are written in PascalCase, not snake_case,
so you might want to rename the model from Ad_company to AdCompany.