Process
- (Lower thread): Text input with start and end dates
- Generate rows: Initialise at Start, then increment by one day (DateTimeAdd) until reach End
- (Upper thread): Summarise countries (group by)
- Append generated dates to country list
- Join with provided data
- Create "passed_exams" field from Right join (initialised at "0")
- Union Join data with Right Join data
- Sort by country and date (this might not be necessary)
- Running total (group by country)
- Sort and cleanup