I have been using MySQL for my school projects, personal web site for years.
My company is using MySQL in all web projects as well.
Now I am thinking to pay for some classes to learn another new Database system, but
I have no idea whether I shall choose MS SQL Server 2008 or Oracle 11g.
I hope to find a better job with high paid salary.
I need some advice and suggestions.
You certainly should not pay in order to learn a new database system. You can get a free version of MS SQL Server Express together with Management Studio on the web. There are loads and loads of materials and tutorials on the web on MS SQL Server. I bet the same can be said about Oracle. In general, go out there and explore the web, it's a much better way to learn than paying for some courses, which might not give you what you need.
if you are a java developer i think Oracle 11g is better, or if you are a .net developer ms sql would be a better choice.
Unless Oracle is giving away downloads of 11G for you to learn on, I'd say that Oracle will be a pricey path to take. They don't list prices that I can see on the web site. (Maybe I didn't look hard enough.) Oracle DBA certification is another expensive proposition. I think it's rigorous, so it might be worth having, but it'll cost you in courses and test fees.
SQL Server won't cost as much. You can download Express for free. I'm sure it won't help you with all the enterprise features that will be missing.
Both MS SQL and Oracle has "express editions" which are somewhat restricted, but free versions that you can try at home. Pick the one you like the most. The salary will depend more on how good you are than the system you pick (why not both?).
It can also depend on your area and what you are trying to get into. It seems like certain segments of the business world use MSSQL or Oracle exclusively. I would say that MSSQL is easier to get into but that's just opinion. Overall it seems like there's more MSSQL jobs but the oracle jobs pay a little better...but again that's a very person experience. I don't think you'd go wrong with either direction. I would agree with the others though that you should just download the free versions and play around a little and see which ones catches your attention more and go from there.
Let's revert roles. I ask the question and you answer.
My question to you is "Should I learn to drive a Ford or should I learn to drive a chevy".
The answer is the same because the question is the same, the tiny and irrelevant difference of problem domain notwithstanding.