I know that this is an old question bumped back up to the front of the line but I agree that it's an important one.
My two cents. With respect to the "mathematics concepts" I'd say to start with
Set Theory and The Relational Model.
Heh... we should definitely do one on "Tuples" as they relate to "Set Theory"... maybe Microsoft will take the hint and finally add an "element ordinal" to the String_Split function.
As for "Relational Model", I'm just happy there are some people out there that know how to get the current date and time using -T-SQL. 😉
The "Relational Model" - which Airfix kit to give to which nephew at Christmas??
The answer is "none". Keep them for yourself... they're fun to build. 😉 If they know the GETDATE() question, buy them a laptop instead. 😉