NoName wrote:
>>If NULL is not a zero length string, then why does Oracle do this? :-
>>SQL> select 'abc'||null from dual;
>>
>>'AB
>>---
>>abc
>>
>>It should return NULL, should it not?
>
>
> I can assure you that empty string <> NULL value.
> According to Oracle 8.0 SQL Reference Manual, Chapter 3, paragraph about
> "Concatenation Operator":
> --- start ---
> Although Oracle treats zero-length character strings as nulls, concatenating
> a zero-length character string with another operand
> always results in the other operand, so null can result only from the
> concatenation of two null strings. However, this may not
> continue to be true in future versions of Oracle. To concatenate an
> expression that might be null, use the NVL function to
> explicitly convert the expression to a zero-length string.
> --- end ---
>
> Regards
>
>
And that's another non-ANSI compliant behaviour...
Look it up: concatenation of a string with NULL yields NULL,
concatenation of a string with an other, empty string yields
the first string
--
Regards, Frank van Bortel
Received on Tue Dec 16 2003 - 15:27:23 CST
