Hello to all
announcing that the beginner with msql

I'm trying to help a friend with a website for your business
I am in a condition with three tables with the same key:

Table: agent, client, schema_provv
Common key agente_id
with a query should update the value num_provv all'agente_id if its customers with agente_id are more than a certain number ....

is this possible?
some kind soul help me