Q2: Where in the specs it tells me to do do start+DOS(of n-1 refill)
(btw 1 minus 1 is not null - it would be zero) for the ETL-derived-prescription row
look: 2 pills for two days. You started April 1st and took the second one the next day. End_date = April 1 + 2 - 1 = April 2
This could be that the duration of drug_supply was reached (in which case drug_exposure_end_date = drug_exposure_start_date + days_supply -1)
null. The same page in spec
Prescription written it is