MySQL, SQL Server, Access, Oracle,Sybase, DB2, and other database systems this are the many options to learn but before learning this some basics of database u can find this on many helpful websites example www.linda.com u can find many tutorials ALL THE BEST!
First try to learn basics of database for that you can take help of books and internet and then try to understand further things.
Firstly, you should try to understand the concepts (data consistency, data redundant, ...) and definitions of database and its components (table, record, field, metadata,...) and then you should learn the syntax of SQL statements from the easiest (create, update, drop database/table/...) to the advanced (procedures, triggers and so many things else). Good luck to u