Some vaguely structured thoughts on the differences that you see between SQL as implemented by one DBMS and that of another.
I have been spending some time with the new, free Oracle Express Edition
This is essentially the same product as Oracle's standard offerings, but it has inbuilt limitations on the amount of user data that it will manage (4GB), number of processors in the server it will utilise (one) and amount of server memory it will use (1GB).
These are relatively minor drawbacks, and I am in the process of building a production web-based application that will use XE as the database back-end. So far and so good - all of the normal SQL, PL/SQL and database interfaces are available, working and performing. I have it installed on my ThinkPad T42 (under Windows XP) and it sits very quietly in the background and doesn't seem to affect anything else that I run.
The installation was very quick and easy. I have coupled it with Oracle SQL Developer
which offers a GUI interface onto the database, allowing you to explore the database objects, insert data directly, run SQL and PL/SQL scripts, export and import data in a variety of ways and so on. Again I am using this on my ThinkPad and have been quite impressed with the interface and its performance. The user interface is not quite in the league of the best that Microsoft can produce, but it is by no means bad.
I look forward to updating you when I find the first problems, or when the application I am building goes live in September.