Cannot overlay Power BI dataset when new columns added to source table

[GerryD]

I am using a SQL database and the import feature. When I add columns to the SQL table in SQL Server and attempt to refresh my dataset in Power BI with the newly added columns, the system does not overlay my existing table but instead, creates a second occurance of that table. I cannot just implement the second occurance since the original table includes measures, etc. How can I overlay the first occurance with the new columns added? Both tables have the same table name. Thanks!   

[Greg_Deckler]

Are you doing this purely within the Service or with Desktop?

[GerryD]

For now, I am developing primarily using the desktop because it appears that the desktop has a more robust feature set.

[Greg_Deckler]

That is a very odd experience then and I'm not sure how that is happening. In my experience, you create the query to the data source and import the data to the data model. Then, if you add columns to the source data, the query picks that up and adds them to the data model. Now, in a lot of cases, if you have added calculated columns, the data refresh will fail and you have to remove all of your calculated columns, refresh and then add all of your calculated columns back, but I have never seen it create an entirely new table on a data refresh of an existing query. That sounds weird.