Add columns to a table or records without duplicates in Duckdb

I have the following code:

import time
from watchdog.observers import Observer
from watchdog.events import FileSystemEventHandler, PatternMatchingEventHandler
import duckdb

path = "landing/persistent/"
global con
con = duckdb.connect(database='formatted/my-db.duckdb', read_only=False)

class EventHandler(PatternMatchingEventHandler):
    def __init__(self, query):
        PatternMatchingEventHandler.__init__(
            self,
            patterns=["*.csv"],
            ignore_directories=True,
            case_sensitive=False,
        )
        self.query = query
    
    
    def on_created(self, event):
        filename = event.src_path.split("/")[-1]
        filename_trunc = filename.split(".")[0]
        try:
            cursor = con.cursor()
            cursor.execute(query.format(filename_trunc), 
                           [event.src_path])
            
            cursor.execute("show tables")
            print(cursor.fetchall())
        except Exception as e:
            print(e)
        finally:
            cursor.close()

query = "CREATE TABLE {} AS SELECT * FROM read_csv_auto(?);"
event_handler = EventHandler(query)
observer = Observer()
observer.schedule(event_handler, path, recursive=True)
observer.start()

try:
    while True:
        time.sleep(1)
        
except KeyboardInterrupt:
    observer.stop()
observer.join()

It basically waits for a file in the path and adds it to the db as a new table. However, I have two extra use cases:

• Add a new csv with the some modifications (with a table already created for that filename) and maybe some rows already exist in the table.
• Add a new csv with a new column (with a table already created for that filename)

However, I don't know how efficiently keep track of these two cases using sql nor duckdb. Any help would be appreciated, thanks.

from Add columns to a table or records without duplicates in Duckdb