Is there a website for online SQL practice?

you can use this one : www.w3school.com

As mentioned above http://www.w3schools.com/sql/ is the most commonly used to beginners/ students.

Yes are there quiet a few, to get started this is the best one, http://www.w3schools.com/sql/

sqlzoo.net

Yes, there are lots of website to practice the SQL..
www.w3school.com is one of the most familiar website for begginer

Better download oracle Express it is free and light.

http://beginner-sql-tutorial.com/sql.htm