Communicating is always better than just learning because you get hands on practical example rather than just leaning. One more importance of learning online through these sites is that you do not have to setup any additional software's on your system.
1. Code School
2. Code Academy
3. Code Avengers
If you want to learn about Structured Query Language(SQL) interactively then start with SQLZOO. They have SQL Engines like MySQL, Oracle, SQL Server, PsotgresSQL, Ingres and DB2. They have quizzes after every tutorials to revise what you have learned. One drawback of SQLZoo is that they do not have hints or suggestions, so if you are stuck on any puzzle you need to search for your answers.
Have you learnt at any of the website above then do share your experience with us. Please Like and Share the CodingDefined Blog, if you find it knowledgeable and helpful.