Jeffry Schwartz looks for exceptions:
Given the complexity, I realized that validating all intermediate and final result sets was essential to ensure that tuning changes did not alter any report results. To support this validation, I saved interim and final result sets into tables for direct comparison.
For these comparisons, the EXCEPT and INTERSECT operators proved invaluable.
Click through for the full story. I’ve always liked using these set operations in ETL jobs because they automatically know how to handle NULL, so this approach is more robust than rigging your own comparisons.