Have you used Oracle ?
For anything,... creating db-driven applications, small tables, etc.

I have used Oracle.
Its in my syllabus (in school), so, i had to learn it anyway.

The SQL commands differ only very slightly from what we use in MySQL.
So, all this PHP & MySQL in fact helped me.

i dont use this ... oracle :P

Nope, i have never used it.

PL/SQL. I'm not keeping up with the latest in the database world, but my wild guess is that this is still the most popular database among giant corporations.

Used it mildly, not real sure I ever got around to any real tables or anything though. It took up too much of my system memory :P. Especially since I dont have a dedicated server.

I never used it.

Oracle (especially the 10 & 11 versions) are memory hogs.
Require at least 1GB ram for smooth functioning.

I have 10g on my 256mb ram computer and while ORACLE is started,
i can't run anything else.

I never used it. Can you tell me what you do in this.

Oracle is a RDBMS similar to MySQL.

We use it to store data.

Big corporations use it as a backend to store their information/data...
example : sales records, project information, employee & payment info, etc.

Oracle > every other RDBMS.

ok...
I am frontend person.
Don't know much about databases. Can only do editing in MySQL and MS access