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Article #25409: What does null mean?

Problem:
What does null really mean?	

Solution:
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Note: The information in this article applies to
           all InterBase versions.
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Null means that the value is not known.  It does not 
mean a blank space or the value 0.  The meaning
of null is frequently misunderstood by users to mean
 blank or zero.  As a result, the statement:

insert into mytable(charField) values '  '; 

will work on a column that has not null defined.  Blank 
is a known value.

Last Modified: 29-SEP-00