> >You're answering your own question: '' (empty string) is NOT NULL.
> >NULL is NULL (empty). An empty string is a value. NULL is a state,
> >so is "NOT NULL".
> >
> IMHO, this unique feature could nearly be considered a bug...

A bug? Why? NULL is NOT an empty string. An empty string
is a value, NULL is a state.

A column can have two states:

NULL
NOT NULL

A string column can have all sorts of values, ranging from an
empty string to pretty much anything you can put into it.

With regards,

Martijn Tonies
Database Workbench - developer tool for InterBase, Firebird, MySQL & MS SQL
Server.
Upscene Productions
http://www.upscene.com