うんと、my.cnfなんだけど。

特にたいしたチューニングはしていない。

ずばり、

vi /etc/my.cnf

# For advice on how to change settings please see
# http://dev.mysql.com/doc/refman/5.6/en/server-configuration-defaults.html
# *** DO NOT EDIT THIS FILE. It's a template which will be copied to the
# *** default location during install, and will be replaced if you
# *** upgrade to a newer version of MySQL.

[client]
port=3306
default-character-set = utf8mb4

[mysqld]
log-bin=mysql-bin
expire_logs_days=14

port=3306
character-set-server = utf8mb4
skip-character-set-client-handshake

インジェクションで使わなくなったらしい

# Remove leading # and set to the amount of RAM for the most important data
# cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.
# innodb_buffer_pool_size = 128M

# Remove leading # to turn on a very important data integrity option: logging
# changes to the binary log between backups.
# log_bin

# These are commonly set, remove the # and set as required.
# basedir = .....
# datadir = .....
# port = .....
# server_id = .....
# socket = .....

# Remove leading # to set options mainly useful for reporting servers.
# The server defaults are faster for transactions and fast SELECTs.
# Adjust sizes as needed, experiment to find the optimal values.
# join_buffer_size = 128M
# sort_buffer_size = 2M
# read_rnd_buffer_size = 2M

sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES

て感じ要するに、絵文字コードが入っても保存できるように4バイトのUTF-8にしてみただけ

mysqlを再起してからmysqlにログインしてみた結果

まあ、いいんじゃないでしょうか。