MYSQL Insert doesn't insert anything

Projects Programming
5 
PubSubClient MQTTclient(espClient);

// Setup up connection to SQL-Server
MySQL_Connection conn((Client *)&espClient);

So, what do you think happens when the MySQL_Connection instance uses the espClient instance to talk to the database? What is the PubSubClient instance supposed to do with that information? And, what is the MySQL_Connection instance supposed to do with the PubSubClient communications?