MySQL code uses a large number of global variables for various purposes: configuration settings, server status information, various data structures shared among threads, and other things. Studying the global variables provides numerous insights on the server architecture. Often the very existence of the variable concisely tells a story about how and why different components work together.
summarizes the most commonly used global variables. Many of those were
moved under the
structure in version 5.0.
Table 3-7. Commonly used global variables
Points to the path of the data directory, which is
set by the
Contains the server version string displayed in the connection greeting and in the log; for example, mysql-4.1.5-log.
Contains the path to the configuration directory
holding the character set definition files. The value is set by
The value gets incremented every time the database
administrator issues the