If you are just starting to work on your certification, I would suggest that you pursue one of the latest certiications on SQL 2012. A certification on 2008 will soon be aged-out.
You can start exploring on this page:
http://www.microsoft.com/learning/en/us/sql-certification.aspx
There you will see the available certifications for SQL Server. I suggest that you start with a MCSA, and then progress into the MCSE if you want a higher-level certification.
Alternetively, if you want a simple, "introductory" certification, you can aim to one the MTA (Microsoft Technology Associate) certifications such as
Exam 98-364: Database Fundamentals:
http://www.microsoft.com/learning/en/us/mta-certification.aspx