On Fri, Sep 30, 2011 at 2:48 PM, John <theu...@gmail.com> wrote: > I believe that there is no real way for you to avoid having to perform > a query for each backend instance. Even in raw SQL, I don't think > there is a way to do what you want - in postgres, for example, you > could not both order by the timestamp and get distinct values based on > backend. >
Sure you can: SELECT backend.*, s1.* FROM backend INNER JOIN status s1 ON backend.id = s1.backend_id LEFT JOIN status s2 ON s1.backend_id = s2.backend_id AND s2.timestamp > s1.timestamp WHERE backend.id IN (1,2,3,4) AND s2.id IS NULL That will extract all the backend info and the status info for the most recent timestamp in a single tuple. The trick is joining to the status table twice and excluding all rows that have smaller timestamps. Remember that SQL is really very powerful, much more powerful than is exposed by the ORM. Cheers Tom -- 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 django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
