> I need to be able to query an object that has a set of related > objects - the query is to find which objects contain the same > set of query objects. For example the main object could be a > research paper and the related object would be a set of topics > that the papers could contain.
This is a popular question that I've found a solution to. It might be kinder in the queryset refactor (Malcolm?), but for the time being, this is what I've used: http://groups.google.com/group/django-users/browse_thread/thread/24de9d4b74935296/ Because of the way the underlying SQL builds the query, you basically end up asking for two contradictory conditions of the same row: WHERE x = 1 AND x = 2 which, as you discovered, returns no rows. The solution I've found is to use an extra() call to build an IN/EXISTS[1] subselect that asks what I want. Thus, it becomes something like WHERE EXISTS( SELECT 0 FROM <innertbl> i WHERE <condition1> AND i.<fk> = <outertbl>.id ) AND EXISTS( SELECT 0 FROM <innertbl> i WHERE <condition2> AND i.<fk> = <outertbl>.id ) -tim [1] FWIW, I've found EXISTS to be faster in PostgreSQL and IN to be faster in SQLServer; haven't profiled MySQL or sqlite. --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
