E.g.: I want the date of the first and last hospital admission for every patient in my table
patient_id and year , to take the sum of a cost variable to create a new variable that represents the total cost for each patient over a given year.encounter_date of each patient; in other words, partitioned on patient_id . This will create two new variables, min_encounter_date and max_encounter_date for each patient. When we run this query, note that no records will be dropped; rather, these new variables will be have consistent values for any given patient_id . min_encounter_date = encounter_date OR max_encounter_date = encounter_date !year ) when defining our partition.