I think the amount of SQL knowledge requirement would be highly dependable on the situation. If it's a larger organization then the requirement might be less because of the amount of peers that can help to teach, and the learning curve may not be as large of an issue. If the person is going in for a solo position than there isn't really room for a learning curve and the requirement would be much higher.
I think from a certification standpoint it would become difficult because there are so many ways to go about the answer as we had just seen. I'd like to pose the question of how do you determine what the 'correct' answer is? Should the proctor have the authority to review incorrect (not matching exactly) answers and deem them acceptable if they still accomplish the answer? What level of depth would the requirements go into; only cover T-SQL that can easily match daily functions, or cover in-depth uncommon tasks such as integration services.
The final question I have would be what would be the different levels of requirements (such as; a general requirements and a specialists requirements, like one specializing in development T-SQL, or specializing in Administration T-SQL), if so how do you then determine the levels?
I guess the different ways to make these determinations will continue to pose more and more questions, really the only foreseen method is to start off with a general requirements test and stem off that as the need is determined from our feedback of how the requirements are meeting our expectations.
~ Without obstacles, you cannot progress ~