re: Are Rules Really a Thing of the Past?

Yes, the postal code rule is a pretty common as it’s easy to explain and relate to. But a business rule can be applied to more complex columns such as a part number, or other designator that’s encoded to permit grouping of like parts. Since the part number is used in many places, having a single place to update the rule is very handy and far safer. If we missed changing a constraint, we’re pooched. We’ve also seen rules applied to choice columns that don’t justify the overhead of a PK/FK. For example, a marriage status can be “Single”, “Divorced”, “Separated”, “Depressed”, “Civil Union” etc. A rule could easily deal with this. Sure, a constraint would work here, but there are situations where a global rule is safer and easier to work with.