Invantive EstateMore information on what SQL is and how it can be used can be found at: http://en.wikipedia.org/wiki/SQL.
The manual on http://sqlzoo.net also gives a good impression. It also enables you to interactively learn how you can retrieve, edit and create data using SQL.
SQL is a standard that has been expanded with extra features by different developers of databases. You can read more about the different types of SQL for each database platform at the following locations:
