[fxn]

IMO an ORM is not a substitute for knowing SQL, much less studying the actual database.

To me, an ORM is a tool that allows someone that knows SQL to write statements they would write by hand using business-level vocabulary.

Also, you have to be savvy enough to know when you are hitting the max expressiveness of the ORM and need some powerful SQL you better write by hand. Active Record certainly provides API for that, and it is an API you are supposed to leverage when the circumstance arises (Rails team over here).