MySQL 04
MySQL Documentation
The documentation for MySQL can be found here.
MySQL vs. Other Databases
MySQL, along with other database systems like MariaDB, Oracle, MSSQL, and PostgreSQL, are relational and use Structured Query Language (SQL). MySQL is open source, along with MariaDB and PostgreSQL.
Usage of MySQL Worldwide
MySQL is the most popular among open source databases. Among all databases, MySQL is the second most popular.
Summary
MySQL, like the other databases that use Structured Query Language, is relational. As for popularity, MySQL is in first place among open source databases and in second place among all databases.