There are in fact alternatives to NULL for outer joins. For example, the SAS data analysis system has an operation akin to a join which gives you an explicit variable saying whether a corresponding row in the joined table was found. In the result of the join, rows where no row was found get zero data values.

Whether you consider that "good" or not is a matter of taste - personally I quite like it because it is very explicit and non-magical and I think NULL semantics cause more problems than they solve.