A Rule Validating Uniqueness within a Single Table

I'm having a tough time trying to get a uniqueness rule working within Information Steward 4.0. My scenario is this:

I have a field or a combination of fields that exist in Table A and I want to validate with a data insight rule that they are unique within Table A.

All the code / references that I have seen up to this point have been using the exist() function with a lookup table, ie two tables involved. My uniqueness rule is only evaluating one table.

If anyone has solved this, it would be awesome to get some example syntax. Thanks so much!!

Tom