***** NOT A TEACHER *****
(1) My books tell me that "whereby" is a rather formal and legalistic term that means "by which."
(a) Here is my bad example: Usingenglish. com has a forum called "Editing & Writing Topics" whereby students may post their
writing, and other members will check their grammar.
(2) "Thereby," my books say, means "as a result of that."
(a) My bad example: The Parser accidentally wrote something political, thereby causing the moderator to delete his post.
(3) If you want good examples, just google some online dictionaries.
P.S. You notice that one must often place a comma (= pause) in front of "thereby."
HAVE A NICE DAY!
Student or Learner