Ken wrote: > I need some advice. I'm struggling with a query that spans 4 tables. > "Struggling" is a bad word; I'll explain later. Django uses a model- > oriented query system together with a Foreign Key manager to get to > the "next" joining table. A query that spans several tables results > in a deeply nested loop. Hence, my struggle. I have an aversion to > writing deeply nested loops. It's an indication that I dont quite > understand my problem. In SQL, you join the tables you need depending > on the query and you filter out entries you are interested in with a > WHERE clause. It's an idea I'm familiar with; it's "flat", ie, not > nested. When I see deeply nested loops, I tend to think recursion. > But that doesnt work either since at each level, the operation is > model-specific. I need some general advice on how folks handle > queries on joined tables within the django framework. Since queries > are model based, is it better to forget about constructing related but > orthogonal tables and simply throw everything in a model? >
I have models: Artist, Track, Album, MultiAlbum (think box set). Artist.tracks is actually the Django created reverse mapping of Track.artist. Once I fully understood the foo__bar__baz notation I found it easier to read and create than the equivalent SQL. The line of code below returns all of the Artists in the chosen multi-album where self.title is the box set's title. Artist.objects.filter(tracks__album__multi__title=self.title).distinct() Hope this helps. If not, perhaps you have some examples of your own to share. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com 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 -~----------~----~----~----~------~----~------~--~---
