GilaMonster (2/17/2014)
Yes.
It's easier with varchar, nvarchar, and varbinary since it's generally not too difficult to convert the primary key to one of those types; other column types could be an issue.
And there's another complication - you need some way of ensuring that the value you convery the primary key into when the column in question has a null never clashes with some other value in that column, which may turn out to be nontrivial.
Tom