Here my challenge:
- I have 4 spreadsheets with more than 100k lines each.
- Each line is a customer and there is the unique ID in column 1, then each sheet has a different set of data (2-3 columns)
- not all the IDs are present in all the spreadsheets
I want to unify all of them in 1 single database, with all data available for each ID.
I guess it's quite easy but I wasted hours trying to get it without success: help please!!

Davide