I'm getting to play with Oracle at work and having a whale of a time in the process. I've only ever had MySQL installed on my home machine, and very nice it is too, but the richer SQL dialect in Oracle is just lovely.
Subqueries are very nice indeed, especially being able to use them in the FROM section (e.g. as inline views), which is wonderfully elegant for certain queries. Admittedly, it also makes your SQL query very long and complicated: I ended up refactoring the queries using proper views... and then realised that MySQL doesn't support this either! I understand that most of what you can do with a subquery you can rewrite with a join, and that views are a form of syntactic sugar, but why refuse to use the expressive power if it's there? (cp Paul Graham's "Beating the Averages")
(OK, the reason to not use the full expressive power of Oracle has always been for me the fact that I'm not paying for the license myself... which is why I'm glad to get the chance to play with it at work.) I really have to look some more at Postgres, which seems to have a lot of the features of Oracle at the same lovely price as MySQL. (Annoyingly it looks like doesn't run on Win32 except with Cygwin).
PostgreSQL is a good choice. Whilst it's not Oracle, it's certianly a very featureful open source database. It does support views and subqueries.
Anyway, whilst there is no official release of PostgreSQL which runs on win32 yet, there is more information about what's happening here.
-Dom
look around for a zip archive of postgres-beta4.zip (ftp://209.61.187.152/postgres/postgres_beta4.zip seems to be dead, but some other mirrors may exist ?). It's from an earlier version of Postgres than the current stable branch, but it's useful if you don't want Cygwin installed to try things out.
As for Oracle SQL, it rules
