Django getting field names from different models - django

Question

Guys,
Is there an easy way to return different fields names from different models by chaining joins?
My model:
Class Item(models.Model):
item_code = models.CharField(max_length=10)
name = models.CharField(max_length=255)
...
Class Stock(models.Model):
item_code = models.ForeignKey( Item )
userid = models.ForeignKey( User )
qty = models.IntegerField()
...
I want to select " Item.Item_code, Item.name, Stock.qty where Stock.userid=2 and Item.item_code = Stock.Item_Code"
How do i do this in Django?
Gath

Answer 1

I want to select " Item.Item_code, Item.name, Stock.qty where Stock.userid=2 and Item.item_code = Stock.Item_Code"
You can pick these specific fields only using one SQL, provided you start from the Stock model. For instance
q = Stock.objects.select_related('userid', 'item_code').filter(
userid__id = 2).values('item_code__item_code', 'item_code__name', 'qty')
This will help if you want to limit the data and then number of queries. If you are not concerned with this then do:
q = Stock.objects.filter(userid__id = 2)
for stock in q:
print stock.item_code.item_code
print stock.item_code.name
print stock.qty
This will return a queryset with only those fields you have chose using values. You can then iterate through it.
PS: Re: your models.
Class Stock(models.Model):
item_code = models.ForeignKey( Item )
userid = models.ForeignKey( User )
qty = models.IntegerField()
...
It is a good idea to use the model name in lower case for FK relationships. For e.g. you ought to write:
Class Stock(models.Model):
item = models.ForeignKey( Item ) # Changed
user = models.ForeignKey( User ) # Changed
qty = models.IntegerField()
...

Answer 2

You can also use this:
Stock.objects.filter(user=2).values('item__item_code', 'item__name')

Answer 3

First of all change fileds names
Read this very carefuly http://docs.djangoproject.com/en/dev/ref/models/querysets/
Class Item(models.Model):
item_code = models.CharField(max_length=10)
name = models.CharField(max_length=255)
...
Class Stock(models.Model):
item = models.ForeignKey( Item )
user = models.ForeignKey( User )
qty = models.IntegerField()
...
#view
stocks = Stock.objects.filter(user=2)
for stock in stocks:
print stock.item.item_code, stock.item.name
#one query version