How do you define global variables in MySQL?

You can define global variables in MySQL using the SET statement. The syntax is as follows:

SET GLOBAL variable_name = value;

In which, variable_name is the name of the global variable to be defined, and value is the value to be set.

For instance, to define a global variable named max_connections and set its value to 100, you can use the following statement:

SET GLOBAL max_connections = 100;

It should be noted that only users with SUPER privileges can define and modify global variables.