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/postfix-files.d/mysql
$shlib_directory/postfix-mysql.so:f:root:-:755
$manpage_directory/man5/mysql_table.5.gz:f:root:-:644
$readme_directory/MYSQL_README:f:root:-:644
Download the raw file with wget or curl
wget -O mysql.example http://exampleconfig.com/static/raw/postfix/centos8/etc/postfix/postfix-files.d/mysql
curl http://exampleconfig.com/static/raw/postfix/centos8/etc/postfix/postfix-files.d/mysql > mysql.example
Other config files you might find useful