Hi Tom,
These are not duplicate entries, indeed. I'm guessing these are dates that are formatted as 'YYYY-MMM'. So, the underlying values are all different, but the formatted representation appears to be the same.
The solution is to create a new field for your Year-Month values, and calculate it in such a way that the values are unique for each Year-Month. Usually it's done in a Master Calendar table. Alternatively, you can add it in the same table where you have the Date field. For example:
LOAD
Date,
Date(MonthStart(Date), 'YYYY-MMM') as YearMonth,
...
This way, the values are going to be unique for each Year-Month.
Cheers,
