A varchar or nvarchar string with length zero isn't NULL, but   
   it doesn't have an ASCII code, since it doesn't have a first   
   character.   
      
   Consider "UPDATE theTable SET acceptor = '' "   
      
   My SQL Server documentation says that ASCII() "Returns the ASCII   
   code value of the leftmost character of a character expression   
   (and by the way, on nvarchar you do want the UNICODE function   
   instead), but doesn't mention this case - no leftmost character,   
   so, ASCII returns NULL.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)