On 10/1/13 6:36 AM, Derek wrote:
We encountered the same problem for a complex model ... we ended up
defining "acceptable" default values that are used instead of
None/NULL, but essentially mean the same thing to the user. (We are
using MySQL which adopts the same approach as Postgresql - I believe
Oracle does it otherwise).
(Just meant for general discussion, not specific to other suggestions in
this thread)
This would seem to be a problem that explicit constraints are meant to
solve. One could check that the row is unique either with or without the
foreign key, depending on whether it is specified. Postgres supports
those very well (others may also nowadays), and if necessary one could
use python or another language supported by the backend to implement
complex logic.
That does not solve the validation problem at the user level, but keeps
invalid data from leaking into the database.
hth
- Tom
On Monday, 30 September 2013 23:17:00 UTC+2, Karen Tracey wrote:
On Mon, Sep 30, 2013 at 4:55 PM, Berndt Jung <ber...@brkt.com
<javascript:>> wrote:
Because the lookup_value of a null field is None, the
validation check is aborted entirely. This seems wrong to me,
and I'm wondering if I'm doing something wrong here.
Redefining the models is not something I can do at this point.
None in Python corresponds to NULL in SQL. SQL defines that NULL
!= NULL. So when checking for unique values the database will not
consider two NULLs to be the same value; the NULLs will be
considered to be different and will not violate the unique
constraint. The Django code is doing the same check for uniquess
that the database will be enforcing. There is no way I know of to
make a database enforce uniqueness among NULL values...
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