Re: Null value is string

And I should have mentioned that setting default null is redundant. When no value is inserted for a column the default *is* null, unless of course there is a not null constraint on that column.

Suzy Vordos wrote:
>
> This example will insert a string value of 'null', which likely isn't
> what you want, nor a good idea. Remove the quotes from null, and the
> column default will instead be a null. Example:
>
> SQL> create table student (student_name varchar2(10) default null);
>
> A null string and a null value are not the same thing, which you can see
> using dump:
>
> SQL> select dump(student_name) from student;
>
> DUMP(STUDENT_NAME)
> ----------------------------
> Typ=1 Len=4: 110,117,108,108 <-- null string
> NULL <-- null value
>
> I once worked with a developer who didn't understand the difference, and
> inserted null strings instead. It was a mess.
>
> Suzy
>
> "donald.holloway" wrote:
> >
> > All,
> >
> > I need to know if there is a way to insert a character value of 'null' as a
> > default for a column:
> >
> > example: student_name varchar2(10) default 'null'
> >
> > I have tried this and it works if I update the column values to the string
> > 'null' later:
> >
> > example: update student set student_name = 'null' where student_name is
> > null
> >
> > I know that null is a reserved word but I though that I saw it used
> > somewhere like this before and just thought I would check with the group on
> > this. thanks.
> >
> > Joseph Hway
> > hway_at_uswest.net
> >
> > --
> > Please see the official ORACLE-L FAQ: http://www.orafaq.com
> > --
> > Author: donald.holloway
> > INET: Donald.Holloway_at_wcom.com
> >
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Suzy Vordos
  INET: lvordos_at_qwest.com

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