On Tue, 2007-03-13 at 08:48 +0100, Roland Hedberg wrote: > Malcolm Tredinnick wrote: > > On Mon, 2007-03-12 at 12:14 +0100, Roland Hedberg wrote: > >> Hi! > >> > >> I have designed a model which contains among other things a couple of > >> DateFields. > >> > >> Some, actually one, of these must have a value but the other may not. > >> > >> So, I tried to use the construct: > >> > >> done_planned = models.DateField(blank=True) > >> > >> But that doesn't work, because I get a exception with the error: > >> > >> "act_activity.done_planned may not be NULL" > > > > You will also need null=True on that field, so that the database can > > store a NULL (no value) in that column. Note that if you just add > > null=True to your model, it will not change the database. You will also > > need to either change the database column by hand or recreate the > > database table. > > Both you and [EMAIL PROTECTED] talks about recreating the > database. For me who know close to nothing about SQL and sqlite3 (which > is what I'm using in this case) it would be interesting if you could > expand on this or, equally good, point me to something that I can read > myself.
Look up the "ALTER TABLE" statement in your favourite SQLite reference. That is the command for changing the types of columns, adding constraints (which is what you want to do here, by adding "NOT NULL" to the column), or adding or removing columns from the table. > I guess this must be a reoccurring topic when you are modeling a new > site since you never get it right the first time around. Quite often when you're initially developing models, you don't have any valuable data in your database, so you can quite happily use the "sqlreset", "sql" and related commands to manage.py to drop and recreate the database tables. Once you have data that you don't want to lose, or are migrating an existing production version to new models, you use "manage.py sql ..." to dump what the SQL should look like, work out the changes from your existing tables and then use things like "ALTER TABLE..." to bring the database into line. Regards, Malcolm --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
