I enjoyed your article as I'm struggling thru the forest heading in the other direction.  I believe there is a need out there for a series of books "Database A for the Database B Developer/DBA".  The series should include helpful tips like a comparison between isnull and nvl.  One thing I found is that a SQL Server isnull(value, '') will return a zero-length string if the value is null where as an Oracle nvl(value, '') seems to return a null.  I'm guessing that Oracle doesn't like zero-length string???

Ona another note -- people that will yell at you without training you are generally not confident or competent in their supposed area of expertice.  They are generally threatened by your questions and are trying to get rid of you.  While it's tough to be in a situation like that, you should take it as a back-handed compliment.  You knew something they didn't and figured out what they new.  You walked out of that situation with twice the knowledge.  That shows character that is worth it's weight in gold.  BTW -- are you looking for work