[Qt-interest] QSqlTableModel NOT NULL constraints and default values

[Tony Rietwyk]

> -----Original Message-----
> Hi all,
> I am using a Postgres table that has some fields defined as
> ....
>  myFld1 character varying(1024) NOT NULL DEFAULT 'my default 
> value'::character varying, 
> ...
> I am using a QDataWidgetMapper with a delegate that converts 
> the data in empty text boxes to NULL instead of ''
> This works with fine with other fields that don't have a NOT 
> NULL constraint.
> 
> When I am trying to use it with a field that has a NOT NULL 
> constraint though, upon submit() I get the error:
> "ERROR: null value in column "myFld1" violates not-null 
> constraint. QPSQL: unable to create query"
> 
> Is there a flag I can set so that the model will allow the 
> query to go to the server, or another solution?
> 
> Thanks,

Hi Harry, 

I haven't used Postgres, but Oracle, Firebird and MSSQL.  In all of those
three, sending NULL to a NOT NULL column will cause a server error.  The
DEFAULT clause is only used when the insert statement does not include the
column.  If you explicitly or implicitly include the column name, then you
must provide a non NULL value.  I'm not sure whether the Qt drivers provide
the field's default value for you - that's probably too DBMS specific.  So
you may need to set that default in your delegate yourself for these fields,
instead of NULL.  

Hope that helps, 

Tony.