Is this an actual Agent? Or are you building this separately in a flow?
Its also really hard to say as you are sort of explaining what you want, but not showing what you have, or the data structures etc. Its difficult to do anything but generalize.
You would have either an automated flow that triggers (depending on how the file is received... email. dropped. etc)
You said in a database, then you said list, so I am not sure what you are storing the full list in.
That being said you have to have a Column, that exists both in your Excel and in your List / Database that lets you do
1) realize its a new row and create the rows
2) updated rows and you can tell which rows to update
So this linkage is important and what we need to drill into
1) You Excel File, we need to see that
2) We need to understand the structure of your database / list and how these things all link together
3) How many different pieces of data is there and are there 1-Many in some cases?
4) How do you determine if something is new or updated?
5) How does a line in the Excel match up to what you put in the database / list?
As a whole you will loop through the Excel, determine if its new or updates and then match that to the row (or create new ones) and do updates or creates.
With more clarity we can help you.
Also, if this is not an Agent, I'd like to move it to the correct forum.
Thanks!
If these suggestions help resolve your issue, Please consider Marking the answer as such and also maybe a like.
Thank you!
Sincerely, Michael Gernaey