Which is the best database to get certification in? Also, is there more demand for C# or Java 2?
The answer to your question depends on what kind of environment you'd like to work in, what type of database activity you'd like to specialize in and what kind of career ladder or development plan you'd like to climb. It's possible to make the argument that any of the leading databases -- among which I'd include Oracle, Microsoft SQL Server and MySQL (in that order) -- would be best for you, depending on how you structure the variables involved. Certification programs of at least one stripe (MS), two stripes (MySQL) and many stripes (Oracle) are available and also worth looking at to help you make your decision.
As for C# versus Java, again that depends on whether you wish to be involved with the Microsoft development camp or the non-Microsoft development camp (which these days includes lots of major companies outside Sun Microsystems, such as IBM and Novell). C# is the way to go if you're in the MS camp; Java if you're in the other camp. There's plenty of demand for both kinds of programmers, but the choice really rests on the platform/development environment that you choose to learn and master (.NET versus J2EE and other Java environments), rather than the language you choose as a consequence of the first decision.
HTH, and thanks for posting,