This is the default example configuration of mysql provided by Postfix. This config file was generated by Postfix running on CentOS 8.
It is located under: /etc/postfix/dynamicmaps.cf.d/mysql
mysql /usr/lib64/postfix/postfix-mysql.so dict_mysql_open
Download the raw file with wget or curl
wget -O mysql.example http://exampleconfig.com/static/raw/postfix/centos8/etc/postfix/dynamicmaps.cf.d/mysql
curl http://exampleconfig.com/static/raw/postfix/centos8/etc/postfix/dynamicmaps.cf.d/mysql > mysql.example
Other config files you might find useful