NULLS and string concatenation

I have a function that uses an execute statement to insert data into a
table, I do in my implementation of table partitioning.

Anyway, I ran into trouble when NULL values were being passed in
(fields are nullable) and my insert statement turned into a big NULL.

Here's an equivalent statement that caused trouble:

select 'some text, should be null:'|| NULL

This returns NULL and no other text.  Why is that?  I wasn't expecting
the "some text.." to disappear altogether.

Is this a bug?

I was able to work around the problem by using COALESCE (and casting
variables since it wants the same data types passed to it).

-Don

-- 
Donald Drake
President
Drake Consulting
http://www.drakeconsult.com/
312-560-1574