First U have a very good base level knowledge on DB. And for this U can start from MS access that comes with Office suit. Then go for the advance level. There are three major softwares to go.
1. MS SQL Server
2. Oracle
3. Open source SQL or My SQL
Opensource SQL or My SQL for web site administration and maintenance.
And If U like any corporate job then you have to choose MS SQL or Oracle SQL
And I recommend U to learn the MS SQL at first then go for ORACLE SQL for better chance.
ORACLE is little different from MS SQL but it is most secure efficient then others.
And for better learning You can chose New Horizon or BASE or get trained from BUET if possible.
But I think the best trainer is nothing but the internet (Youtube, Facebook, database blogs etc).