SQL exercises - Help the user to gain or improve skills in building query statements. A rating system is supported for SELECT exercises and certification. English and Russian versions of an SQL handbook are also available. SQLCourse - An interactive tutorial providing easy-to-understand instructions, with a live query interpreter and practice database. SQLCourse2 - A follow-up to SQLCourse, with tutorials on more advanced aspects of the language, featuring a live interpreter and database with which to test commands. SQLZOO - A step-by-step tutorial with live interpreters, allowing access to tables using any of Oracle, SQL Server, MySQL, Access or PostgreSQL engines. Database and SQL eLearning - Database theory and an online tutorial interface to an Oracle database system, allowing a user to learn interactively. The site automatically checks and marks query strings, and gives instant feedback. Kihlman's SQL (Graphic SQL tutorial) - A shareware program that helps you learn SQL. The user writes their own statements or can take a test, and the tests take the user through various levels of difficulty. SQL Quiz - An online quiz to test and improve a user's database knowledge, giving a score and the correct answers on completion. SQL Fiddle - Application for testing and sharing SQL queries.