Null value in not null field is actually logical corruption,
so applications should not encounter it under normal circumstances ...

> Thanks, that explains everything. I think we should definitely
> consider to change isql's behaviour here

... but yes, tools like isql should display it correctly always,
to avoid confusion.

> (and maybe even the default
> engine behaviour),

Default behaviour can't be changed, because the same mechanism
is used by application to distinguish nullable/not nullable fields.

>> You can try FSQL tool from this site
>> http://www.volny.cz/iprenosil/interbase/
>> it will show null state correctly.
>
> Very good. You just earned yourself - and FSQL - a luxury seat in the
> new Null Guide :-)

Christmas present :-)

Ivan