By default queries in Oracle are case sensitive. There are ways to achieve case insensitivity, but each way has its advantages and disadvantages.
Assuming that your SQL code doesn't utilize MySQL-specific syntax, then you should be able to port your SQL with minimal (if any) problems. Simple table joins and "group by" functionality should be easy to port. However, if your code does take advantage of MySQL-specific features, then expect to do some syntax tweaking.
-- Michael
Darkstreak Consulting
www.darkstreak.com