django admin missing records

Question

I have a company_images table that belongs to country_master except when country_id is 0 . If country_id is 0 i am assuming it's 'all locations'. But since 0 doesn't exist in country_master. It returns no result for those entry in company_images listing. How do i fix it.

Forgive me if this is a simple thing coz i am new to python/django.

Model.py

class CountryMaster(models.Model):
    country_id = models.IntegerField(primary_key=True)
    country_name = models.CharField(max_length=255)
    created_date = models.DateTimeField(auto_now_add=True)
    updated_date = models.DateTimeField(auto_now=True)

    class Meta:
        db_table = "country_master"

    def __unicode__(self):
        if self.country_name is None:
            return "None"
        else:
            return self.country_name


class CompanyImage(models.Model):
    image_url = models.ImageField(upload_to='company', max_length=255)
    country = models.ForeignKey(CountryMaster)
    created_date = models.DateTimeField(auto_now_add=True)
    updated_date = models.DateTimeField(auto_now=True)

class Meta:
    db_table = "company_images"

def __unicode__(self):
    return "None"

I have tried this and mentioning this in admin.py as a display filed

def country_name(self):
    if self.country_id is 0:
        return "ALL"
    else:
        return self.country
country_name.short_description = 'Country' 

Answer 1

One work around is, make country field nullable ( null=True, blank=True ) and if empty, assume all locations. That, in my opinion would be cleaner.

Another approach would be to create a CountryMaster object (as a fixture) for the all option - In other words, a fixture that loads to the database, a CountryMaster object with name=all . So, whenever the user selects all , you can assign the reference to this object.