On 1/11/08, Helen Borrie <[EMAIL PROTECTED]> wrote:
> >OK, now I see. I missed, that the column will be evaluated only for
> >column definition without domain.
>
> Incorrect. All column definitions have a domain, including those that are
> defined independently of a user-defined domain. All of the domain
> definitions are stored in RDB$FIELDS. The column RDB$FIELD_SOURCE in
> RDB$RELATION_FIELDS points to the name of the domain in RDB$FIELDS, viz.,
> RDB$FIELD_NAME. The nullability check is performed on the record that stores
> the domain definition, i.e. RDB$FIELDS.RDB$NULL_FLAG.
>
I know this. I was just responding to "request" for new column
SET_NOT_NULL (which I still don't know why should be usefull, but
...).
> Just make sure you understand
> a) the difference between NULL and nullable
> b) that "nullable" means the field is allowed to be null: it does not mean
> that it is always null; while "non-nullable" will always mean that the field
> has been constrained to be NOT NULL
> c) that the VALUE of 1 on RDB$FIELDS.RDB$NULL_FLAG means that the field is
> NOT nullable and that the nullABLE flag does not have the value 0: it is
> null.
> d) that there will be more potential for confusion in the code, in case the
> GetSchema call is reading the null indicator field (sqlind) directly from the
> output descriptor: after the query on the system tables has been prepared,
> sqlind will be -1 if the field is nullable, or 0 if it is non-nullable.
>
I'm completely clear with this behavior. I'm using
RDB$RELATION_FIELDS.RDB$NULL_FLAG and RDB$FIELDS.RDB$NULL_FLAG in my
"create ddl for table" apllication and works like a charm and same as
isql. :)
--
Jiri {x2} Cincura (Microsoft Student Partner)
http://blog.vyvojar.cz/jirka/ | http://www.ID3renamer.com
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