Is there a way to switch the data source from Google Sheets to MySQL without rebuilding the whole app?
Yes! From my testing, so long as the data source is exactly the same structure, you can simply change the data source table by table… you can also copy the app and change the source to MYsql @Harry
Keith, clicking on the source in the table definition allows you to select a different table source. If they both havs the same structure, you are good.
But since you are going from Sheets to mySQL tables, your best routw would indeed be to copy the app and select the mySQL data source for the copy (this will create the tables with the appropriate data in them)