Create a "common name" field to db based on the content of existing field

Hi everyone, I have a few influxdb files stored in aws, and I would like to add a common name field to each database based on the content of an existing field in the database. I am a complete novice at this type of operation, so be gentle…thanks in advance…once (and if) I’m able to acheive this, I will setup the export from node red to automatically do this from this point. Hope that makes sense.
Regards, Andrew.