Why do Oracle treat NULL like this?

Hi,

select 'a' || NULL || 'b'
from dual
gives 'ab'

but

select 1 + NULL
from dual
gives NULL

Why in the first example, NULL is considered as empty string, while in the second example NULL is considered as undefined? That does not look consistent. What is the rationale behind it?

Thanks in advance.
Michael Received on Wed Mar 29 2000 - 12:07:29 CST