On Fri, 14 Feb 2014 20:13:43 +1000 Nick Coghlan <ncogh...@gmail.com> wrote: > On 14 February 2014 20:02, Antoine Pitrou <solip...@pitrou.net> wrote: > > On Fri, 14 Feb 2014 10:46:50 +0100 > > Lennart Regebro <rege...@gmail.com> wrote: > >> > > >> > Sending this to python-dev as I'm wondering if this was considered when > >> > the > >> > choice to have objects of different types raise a TypeError when > >> > ordered... > >> > > >> > So, the concrete I case I have is implementing stable ordering for the > >> > python Range objects that psycopg2 uses. These have 3 attributes that can > >> > either be None or, for sake of argument, a numeric value. > >> > > > [...] > >> > >> It was considered. It's not obvious where you want "None" to appear in > >> your ordering, so you will have to implement this by yourself. I can't > >> come up with anything obviously shorter. > > > > I have to agree with Lennart. The fact that SQL defines an order for > > NULL and other values doesn't mean it's obvious or right in any way (I > > never remember which way it goes). > > SQL doesn't define an order for NULL, it's more like a "quiet NaN" - > if either operand is NULL, the result is also NULL. (I ran into this > recently, in the context of "NULL == value" and "NULL != value" both > being effectively false).
Hmm, it seems you're right, but I'm quite sure some DBMSes have a consistent way of ordering NULLs when using ORDER BY on a nullable column. Regards Antoine. _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
