FreeTDS Development Group

["Bort, Paul" <pbort AT tmwsystems.com>]

> 
> Ahem.  I understand they're technically different, of course, 
> but how are
> they semantically different?  Which user can tell the 
> difference between a
> null field and a zero-length string?  And what is the 
> difference between
> an empty field and a field that's empty?  
> 

Just a quick example from my current project of how '' and NULL are
different and that difference can be important:

We have a table that holds user settings, and a null ( or a missing row
) means that the default (from a separate table) should be used. OTOH,
if the column is an empty string, that means that the setting should be
an empty string, even if the default says otherwise. If a setting is a
file prefix, an empty string is a reasonable value.