The official term is non equijoin but unequal sounds a little more descriptive to me. In FileMaker, the define relationship dialog box got a nice boost. You can have a choice of operators other than equal to ... for example you can have ...
≠ ( not equal )
> ( greater than )
< ( less than )
≥ ( greater than or equal to )
≤ ( less than or equal to )
x ( means all records in both table occurrence compare, no matter the data in either )
FileMaker allows you to create relationships that comprise of more than one comparison layer. This can be very handy when building date range related comparison using the new greater than and less than operators. Say you have two global date fields, one called start date and one called end date. One layer of the relationship could be greater than start date and that would normally return a set of related records. Add to this a second layer of less than end date and you have a range of related records!
You could add yet another layer that could say, day ≠ ( not equal ) Saturday and add another layer to say day ≠ ( not equal ) Sunday ... and ... the returning related records would be week days!
Here is an example of a multiple layer compare in action!