This further illuatrates my point. An exceptional DBA that can answer 'why' must be able to research the subject. They must know what the right question is to ask, and where to go to get the answer.

Research skills and resource knowledge is the most important skill. As you stated with your teachers, the exceptional teacher(s) had explained the 'why'. This can only be perormed by further researching to find out 'why' the calculation is made.

An effective communicator can definitely move things along faster and smoother. Without the knowledge from researching the subject, they'd be ineffective to explain 'why'.

Thanks,

James