SQL Book and Reference


MySQL Tutorial MySQL tutorial site provides you useful tutorials of SQL and MySQL.
SQL on Wikipedia SQL information on Wikipedia with definition of SQL, SQL history and other languages elements
SQL Tutorial Yet another SQL tutorial site, it mainly focus on SQL standard with practical examples

SQL Database - RDMBS


IBM's Database - DB2 RDMBS's product from IBM
Microsoft SQL Server Microsoft SQL Server is an enterprise database management system from Microsoft. It uses mainly T-SQL as the query language.
MySQL The world most popular open source database
Oracle The world's largest enterprise database software
PostgreSQL The world's most advanced open source database