Question

This should be really simple, I could do it without thinking on traditional SQL but can’t get it with Django models!

I have a model with two foreign keys to create many to many relationship – I am not using many to many field in Django

class Story(models.Model):
   title = models.CharField(max_length=200)
   pub_date = models.DateTimeField('date published')

   def __unicode__(self):
      return self.title

class Category(models.Model):
   categoryText = models.CharField(max_length=50)
   parentCat = models.ForeignKey('self',null=True,blank=True)

   def __unicode__(self): 
      return self.categoryText

class StoryCat(models.Model):
    story = models.ForeignKey(Poll,null=True,blank=True)
    category = models.ForeignKey(Category,null=True,blank=True)  

    def __unicode__(self):
      return self.story

I would like to query for a category like ‘short’, and retrieve all the unique keys to all stories returned.

c=Category.objects.get(categoryText=’short’)

s=StoryCat.objects.get(category=c)

when I try this I get an error that multiple rows were returned. I actually want to just retrieve the id values but I don’t seem to be able to figure how to do this.

How can I get the id values that are returned?

Answer 1

“multiple rows were returned” is because you are using get rather then filter on either or both of the queries.

If there is only one category matching short try:

c = Category.objects.get(categoryText='short')
s = StoryCat.objects.filter(category=c)

If it is possible for there to be more then one category try something like the following:

# get just ids via values_list
cids = Category.objects.filter(categoryText='short').values_list('id', flat=True)

s = StoryCat.objects.filter(category__id__in=cids)