Null and concat

[Ivan Smahin]

Hello Thorsten,

Friday, October 5, 2007, 6:05:00 PM, you wrote:

> Hi Ivan,

> On 2007-10-05, at 16:50, Ivan Smahin wrote:
>> Could you send me that db?
> before sending the db again ...

>> I tried to reproduce it - but it works as expected.
>>
>> --
>> CREATE TABLE "t1" (
>>         "f1" STRING (20) ,
>>         "f2" STRING (20) ,
>>         "m1" STRING (20) METHOD ('concat( f1, f2 )') );

> I've got only varchar fields, could this be a difference?
Certainly no.

>>> Furthermore I then expect that NULL are always handled as empty
>>> string in any string operation.
>>
>> Null means indeterminacy.

> yes, that's clear to me, BUT I'm talking about that the NULL value  
> should always been treated in the same way, not about the meaning of  
> a null value.

Concat() returns null if any of argument calculated to null value.

BTW,
Any rule has own exceptions...
Example  - count(f1) ignores null values rather then count(*). Yes, it
is a special sign for special goal, but there is common rule violation...


-- 
Best regards,
Ivan Smahin 
Senior Software Engineer
Paradigma Software, Inc
Valentina - The Ultra-Fast Database
http://www.valentina-db.com