query-question

hello,

I'm facing an odd problem.
I have a query:

SELECT "Kürzel", "Autor(en)", "Titel"
FROM "tblTitelangaben"
WHERE "Titel"||"Kürzel"||"Monographie-Kürzel"||"Autor(en)" ILIKE '%er%';

this works like a charm.

but if I add another ||"something" - which might be emtpy, I get no
results.. why?

WHERE
"Titel"||"Kürzel"||"Monographie-Kürzel"||"Autor(en)"||"Herausgeber"
ILIKE '%er%';

|| is the same as "OR", is it not?

1 OR 0 = 1
1 OR 1 = 1
0 OR 0 = 0
right?
therefore I should get the same, or more results...

any hints are greatly appreciated!

TIA,
alex