Re: Null value is string

From: Suzy Vordos <lvordos_at_qwest.com>
Date: Tue, 09 Jul 2002 16:03:20 -0800
Message-ID: <F001.0049318A.20020709160320@fatcity.com>

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
>
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> --
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>
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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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Received on Tue Jul 09 2002 - 19:03:20 CDT