Hi Ahsan
As there are a gazillion books on SQL this question is similar to "Which is the best ice cream: vanilla or chocolate?" 
Personally I like "DATABASE IN DEPTH: RELATIONAL THEORY FOR PRACTITIONERS BY Date, Chris J.(Author)05-2005( Paperback )" as it provides a rock solid understanding in what you can do and what you cannot do with relational databases without messing up your logic.
And to get hands-on approaches, have a look into any of Joe Celkos books.
Cheers, Lars