> i've just tried the following:
> SELECT whatever FROM table WHERE column <> '1'
> revealing that no rows are returned that have column=NULL.

http://www.networkcomputing.com/netdesign/1213sql22.html contains an explanation 
(search for 'NULL Values' near the middle of the page). The short answer: NULL means 
'unknown', so a NULL column might contain '1' once the value is known. 

You might also search the Web for 'three valued logic'.

Daniel Dittmar

-- 
Daniel Dittmar
SAP DB, SAP Labs Berlin
[EMAIL PROTECTED]
http://www.sapdb.org/
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