I've just started to learn how to do queries in my Django application, and I have a query that gets me the list of new users filtered by the date joined:
newUsers = User.objects.filter(is_active=True).order_by("-date_joined")
This as I understand it gives me ALL the users, sorted by date joined. How would I best limit it to get me the last N users?
On this, does anyone recommend and reading material to learn more about these types of queries?
User.objects.filter(is_active=True).order_by("-date_joined")[:10]
will give you the last 10 users who joined. See the Django docs for details.
you can use list slice operation on constructed queries e.g.
For example, this returns the first 5 objects (LIMIT 5):
Entry.objects.all()[:5]
This returns the sixth through tenth objects (OFFSET 5 LIMIT 5):
Entry.objects.all()[5:10]
Read django documentation http://docs.djangoproject.com/en/dev/topics/db/queries/
BTW, if u would just divide amount of all user, (for example, 10 per site) you should interest pagination in dJango, very helpful http://docs.djangoproject.com/en/dev/topics/pagination/#topics-pagination
User.objects.filter(is_active=True).order_by("-date_joined")[:10]
QuerySets are lazy [ http://docs.djangoproject.com/en/dev/ref/models/querysets/ ]. When you're slicing the list, it doesn't actually fetch all entries, load them up into a list, and then slice them. Instead, it fetches only the last 10 entries.