How to calculate Days_supply in drug_exposure table when you have Start_date and End_date in source with following conditions -
End_date is not Null
End_date is Null
Also , We have Refill data but its Alphanumeric in nature
If you have no end date obviously you cannot calculate days_supply. You either guess it (most of them are 30 days), or you leave empty.
Parse it and fill the fields. You’d add a ton of value because it becomes computable.