Masters or another Bachelors??

[AngryPeruvian]

Hello, 

I recently graduated in May 2015 with a bachelors in International Affairs. Thankfully I have been able to find a decent job, even though it makes me miserable. I feel like I majored in the wrong field, and I wish to start a career in Information Systems. I love working with databases. I enjoy using SQL and Hadoop. Should I go and get a Masters in MIS/MBA with an MIS concentration(so I can be more well-rounded) or should I go back and get a second bachelors? The Masters/MBA would be more expensive, but would probably take only a year and a half longer to get. 

Thanks