Hi, I read about MySQL, Oracle, SQL Server [Express edition]. I don't know what else is there. My requirement is

1) I must be able to use in my server for publishing and locally for development

2) My site will have lakhs of questions so it should be easy to search

3) I want the database to be free. I am not going to re distribute the database. I just use it in my server for storage

4) I would like to have good UI

So What is the best choice? And what else is there? What are the restrictions especially?