MySQL in a Nutshell [3]
Chapter 1. Introduction to MySQL
MySQL is an open source, multithreaded, relational database management system created by Michael “Monty” Widenius in 1995. In 2000, MySQL was released under a dual-license model that permitted the public to use it for free under the GNU General Public License (GPL); this caused its popularity to soar. The company that owns and develops MySQL is MySQL AB (the AB stands for aktiebolag, the Swedish term for stock company), which is now a subsidiary of Sun Microsystems. Currently, MySQL AB estimates that there are more than 6 million installations of MySQL worldwide, and reports an average of 50,000 downloads a day of MySQL installation software from its site and from mirror sites. The success of MySQL as a leading database is due not only to its price—after all, other cost-free and open source databases are available—but also its reliability, performance, and features.
The Value of MySQL
Many features contribute to MySQL’s standing as a superb database system. Its speed is one of its most prominent features. In a comparison by eWEEK of several databases—including MySQL, Oracle, MS SQL, IBM DB2, and Sybase ASE—MySQL and Oracle tied for best performance and for greatest scalability (see http://www.mysql.com/it-resources/benchmarks for more details). MySQL is remarkably scalable, and is able to handle tens of thousands of tables and billions of rows of data. Plus, it manages small amounts of data quickly and smoothly.
The storage engine, which manages queries and interfaces between a user’s SQL statements and the database’s backend storage, is the critical software in any database management system. MySQL offers several storage engines with different advantages. Some are transaction-safe storage engines that allow for rollback of data. Additionally, MySQL has a tremendous number of built-in functions that are detailed in several chapters of this book. MySQL is also very well known for rapid and stable improvements. Each new release comes with speed and stability upgrades, as well as new features.
The MySQL Package
The MySQL package comes with several programs. Foremost is the MySQL server, represented by the mysqld daemon. The daemon listens for requests on a particular network port (3306 by default) by which clients submit queries. The standard MySQL client program is simply called mysql. With this text-based interface, a user can log in and execute SQL queries. This client can also accept queries from text files containing queries, and thereby execute them on behalf of the user or other software. However, most MySQL interaction is done by programs using a variety of languages. The interfaces for C, Perl, and PHP are discussed in this book.
A few wrapper scripts for mysqld come with MySQL. The mysqld_safe script is the most common way to start mysqld, because the script can restart the daemon if it crashes. This helps ensure minimal downtime for database services. The script mysqld_multi is used to start multiple sessions of mysqld_safe, and thereby multiple mysqld instances, for handling requests from different ports, and to make it easier to serve different sets of databases or to test different versions of MySQL.
MySQL also comes with a variety of utilities for managing a MySQL server. mysqlaccess is used for creating user accounts and setting their privileges. mysqladmin can be used to manage the MySQL server itself from the command line. This interaction includes checking