MySQL / SQL

• Official MySQL Documentation – The MySQL Reference Manual covers most areas of MySQL use. This manual is for both MySQL Community Server and MySQL Enterprise Server. If you cannot find the answer(s) from the manual, you can get support by purchasing MySQL Enterprise, which provides comprehensive support and services.
• PhpMyAdmin – phpMyAdmin is a tool written in PHP intended to handle the administration of MySQL over the Web. Currently it can create and drop databases, create/drop/alter tables, delete/edit/add fields, execute any SQL statement, manage keys on fields, manage privileges,export data into various formats and is available in 50 languages. GPL License information.
• PosgreSQL docs – PostgreSQL is a powerful, open source relational database system. It has more than 15 years of active development and a proven architecture that has earned it a strong reputation for reliability, data integrity, and correctness.
• PhpPGAdmin – phpPgAdmin is a web-based administration tool for PostgreSQL. It is perfect for PostgreSQL DBAs, newbies and hosting services.
• SQL Notes – Some helpful hints on administrating and working with major linux sql-databases.