Comment by ErwinSmout

What they "called out as flawed" was the impossibility to declare any such rule with SQL as it stood. What they were "criticizing" was precisely the fact that a data language that was supposed to be "expressively complete" was *unable* to express such a rule. You can't claim "expressive completeness" for a language if there is demonstrably a case where said language's expressiveness fails to meet the mark. It's not the "behaviour of the language" they were criticizing in all/any of those use cases that were supported by the language as it stood. They were criticizing the fact that there was a use case [and a relatively reasonable one on the face of it] that the language couldn't support.