// How to repeat

[root@cluster-repo mysql-advanced-5.6.20]# bin/mysql -u root -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 15467
Server version: 5.6.20-enterprise-commercial-advanced-log MySQL Enterprise Server - Advanced Edition (Commercial)

Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> truncate performance_schema.events_statements_history_long;                                                                                                                                Query OK, 0 rows affected (0.01 sec)

mysql>  select sql_text from performance_schema.events_statements_history_long;
+------------------------------------------------------------+
| sql_text                                                   |
+------------------------------------------------------------+
| truncate performance_schema.events_statements_history_long |
+------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> \q
Bye

// Just put some random thing to mysql

[root@cluster-repo mysql-advanced-5.6.20]# cat /dev/urandom|head -c 100 | bin/mysql -uroot -p --force
Enter password:


// Confirm that it indeed warns

[root@cluster-repo mysql-advanced-5.6.20]# bin/mysql -u root -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 15733
Server version: 5.6.20-enterprise-commercial-advanced-log MySQL Enterprise Server - Advanced Edition (Commercial)

Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> set names utf8mb4;
Query OK, 0 rows affected (0.00 sec)

mysql>  select sql_text from performance_schema.events_statements_history_long;
+------------------------------------------------------------------------+
| sql_text                                                               |
+------------------------------------------------------------------------+
| truncate performance_schema.events_statements_history_long             |
| select sql_text from performance_schema.events_statements_history_long |
| NULL                                                                   |
| select @@version_comment limit 1                                       |
|                                                                       |
| NULL                                                                   |
| select @@version_comment limit 1                                       |
| select sql_text from performance_schema.events_statements_history_long |
| show warnings                                                          |
| set names utf8mb                                                       |
| set names utf8mb4                                                      |
+------------------------------------------------------------------------+
11 rows in set, 1 warning (0.00 sec)

mysql> show warnings;
+---------+------+-----------------------------------------------------------------------------------+
| Level   | Code | Message                                                                           |
+---------+------+-----------------------------------------------------------------------------------+
| Warning | 1366 | Incorrect string value: '\xDD\xFB*\xB5\xC2\x19...' for column 'SQL_TEXT' at row 5 |
+---------+------+-----------------------------------------------------------------------------------+
1 row in set (0.00 sec)