SHOW VARIABLES;
-- или 
SELECT * FROM PERFORMANCE_SCHEMA.SESSION_VARIABLES;

mysql> SHOW WARNINGS;
+---------+------+----------------------------------------------------------------------------------+
| Level   | Code | Message                                                                          |
+---------+------+----------------------------------------------------------------------------------+
| Warning | 1366 | Incorrect string value: '\xE7\xE8\xEC\xE0)' for column 'VARIABLE_VALUE' at row 1 |
+---------+------+----------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT *, HEX(VARIABLE_VALUE) hex_codes FROM PERFORMANCE_SCHEMA.SESSION_VARIABLES ORDER BY VARIABLE_NAME LIMIT 622,1;
+-----------------+---------------------------+----------------------------------------------------+
| VARIABLE_NAME   | VARIABLE_VALUE            | hex_codes                                          |
+-----------------+---------------------------+----------------------------------------------------+
| thread_handling | one-thread-per-connection | 6F6E652D7468726561642D7065722D636F6E6E656374696F6E |
+-----------------+---------------------------+----------------------------------------------------+
1 row in set, 1 warning (0.01 sec)