When we fire a query will only fetched data go into bufferpool OR scanned/joined data OR grouped/sorted data OR all tables entire data in FROM clause. Will the query be stored in bufferpool and the fetched data mapped to the query? What happens if data involved in query is modified? On what condition/situation the hard disk is used for query when it is fired second, third etc. time? These are all related questions, hence I am asking under a common title & have given suitable points as well.