Re: How to create unique constraint on NULL columns

> Then redesign this as a many to many relation.  That way someone can
> have access to one, two, three, four, or all departments.

This means adding separate row for each department into permission table.
If new department is added, I must determine in some way users which are
allowed access to all
departments and add nw rows to permission table automatically.

It seems more reasonable to use NULL department value as "do'nt know, all
departments allowed"

Andrus.