You said you had watched the Essentials Guide videos, but I am sure there would be help with that question there. Also see this page from the docs. Working with messages : Node-RED
I notice that your query appears to have returned a string for volt1. Does that mean that you are writing string values to database for something that is actually a number. If so then that is a bad idea. Make sure you provide it to influx as a Number not as a String. Unfortunately I think that means you will have to DROP the measurement and start again as it is not possible to change the field type once the field has been created.
