Subject Firebird mentioned at www.dbdebunk.com :-) ... Nulls in Unique Indices
Author Martijn Tonies
http://www.dbdebunk.com/page/page/772081.htm

With regards,

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