Subject RE: [Firebird-Architect] unique constraint on NULL column?
Author Dmitry Yemanov

> I have found that firebird does not allow an unique contsraint to be
> defined on a NULLable column. This is a different behaviour to other
> DBs. Will this be changed in firebird 1.5?

It's already changed to conform the SQL200n specification, i.e. FB 1.5
supports unique constraints for nullable columns.