On Tue, Aug 4, 2009 at 5:17 AM, Javier Guerra<[email protected]> wrote: > > Hi all, > > > I've just upgraded to 1.1 (congrats everybody!), and want to put the > aggregation/annotation features to use. but it doesn't seem to be a > way to annotate the records with counts of different subsets of > related records. > > my problem: i have 'Order' and 'Item' models, and the items can be > on several states or processing: > > class Order (models.Model): > order_no = models.Integerfield() > date = models.DateTimeField() > client = models.ForeignKey (Client) > > class Item (models.Model): > order = models.ForeignKey (Order) > description = models.CharField (max_length=50) > price = models.DecimalField (max_digits=7, decimal_places=2) > quantity = models.IntegerField() > status = models.SmallIntegerField() > > and I want to show a list of all the orders, with columns showing how > many items are on each state: > > | order | client | not yet | processing | ready | > -------------------------------------------------------- > | 000001 | Jon Doe | 5 | 4 | 0 | > | 000002 | Jane Smith | 2 | 7 | 3 | > -------------------------------------------------------- > > so far, i only found how to add a column with the total number of items: > > Order.objects.annotate(Count('item')) > > but i can't count subsets of items. Is there any way to do that in > the DB, or I have to do it in Python?
Yes, there is a way to do this in the database - but no, there isn't a way to use Django's aggregation features to expose the capability. To achieve this in SQL, you need to add an inner query for each summary column you want; each summary column filters the result set to the subset of items you want; then join those inner tables with the master results table. Yours, Russ Magee %-) --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~----------~----~----~----~------~----~------~--~---
