> Can you define "nested queries"?

I haven't seen the code yet that he's referring to, and if you'd like I can get back to you once I do.

I believe what he must be talking about, though, is something like this:

SELECT *               ;
  FROM Customers       ;
  WHERE iInvID IN      ;
    (SELECT iInvID     ;
      FROM Invoices    ;
      WHERE iPartID IN ;
      (SELECT iPartID  ;
        FROM Parts     ;
        WHERE iPartID = 25))

Are you familiar with this limitation and its reasons?