MySQL wait_timeout Variable - GLOBAL vs SESSION

Question

SHOW VARIABLES LIKE \"%wait%\"

Result: 28800

SET @@GLOBAL.wait_timeout=300

SHOW GLOBAL VARIABLES LIKE \"%wait%\"

Result: 300

SHOW SESSION VARIABLES LIKE \"%wait         


        

Answer 1

Your session status are set once you start a session, and by default, take the current GLOBAL value.

If you disconnected after you did SET @@GLOBAL.wait_timeout=300, then subsequently reconnected, you'd see

SHOW SESSION VARIABLES LIKE "%wait%";

Result: 300

Similarly, at any time, if you did

mysql> SET session wait_timeout=300;

You'd get

mysql> SHOW SESSION VARIABLES LIKE 'wait_timeout';

+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| wait_timeout  | 300   |
+---------------+-------+