Database URL: jdbc:mysql://${mysql_hostname}:${mysql_port}/${mysql_database}
JDBC Driver Class: com.mysql.jdbc.Driver
Username: ${mysql_username}
Password: ${mysql_username}

Database URL: jdbc:mysql://${__P(mysql_hostname,)}:${__P(mysql_port,)}/${__P(mysql_database,)}
JDBC Driver Class: com.mysql.jdbc.Driver
Username: ${__P(mysql_username,)}
Password: ${__P(mysql_password,)}

mysql_hostname=localhost
mysql_port=3306
mysql_database=test
mysql_username=johndoe
mysql_passowrd=secret

jmeter -Jmysql_hostname=localhost -Jmysql_port=3306 -Jmysql_database=test -Jmysql_usename=johndoe -Jmysql_password=secret