Dave: Ah yes *slap in the forehead*. I had forgotten that you could add additional fields using extra() and sort by them. Thanks for your solution. Don: Excellent point. I hadn't considered the behavior of other aggregate functions and things could get quite messy handling the many, different behavioral cases.
Thanks for your help! On Dec 14, 11:30 am, Don Arbow <[EMAIL PROTECTED]> wrote: > On Dec 14, 2006, at 12:49 AM, MC wrote: > > > > > > > > > Problem: > > I order dates andnullvalues in ascending order under MySQL. To my > > surprise,nullvalues are listed first, then actual dates. Turns out > > that in MySQL,nullvalues are LOWER than non-nullvalues, whereas > > Postgresql is the reverse. As outlined here > >http://troels.arvin.dk/db/rdbms/#select-order_by, it seems the only > > way > > to reverse the order is by prepending a - sign and switching from ASC > > to DESC. Unfortunately, this is the same syntax Django uses for > >ordering! > > > Solution: > > I couldn't think of an easy solution through the model API or using > > custom managers. I suppose I could write custom SQL, but it would be > > nicer to use the model API. I could use a default value like the year > > 3000 and filter for display. Any suggestions? Thanks for your help!Under > > relational database theory, nulls are not less than or greater > than any value, including other nulls. Because of this, you should > never count on where a particular database puts those values. The > page you quoted explains the allowances that database authors have > made to work around the problem. The page didn't even mention sqlite, > which follows mysql's convention. > > I would say this is something that Django should stay away from, too > many differences, even more when you include aggregates such as min() > and max(). For example in Postgres, min() and max() ignore nulls in > columns unless all column values arenull, so this behavior is not > consistent with its column sorting routines. I think If you want > minimum or maximum values in your tables, they should be explicitly > coded. > > Don- Hide quoted text -- Show quoted text - --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
