I have a dataset that is submitted each month. It consists of a list of teachers and the classes they teach. If a teacher shows up in one class list for this month and they don't show up in the class for next month, the endDate of the column for the newly merged dataset will be updated. How do I update the endDate column of the merged dataset. In my example , the teacher with id 1 did not show up for class B in februrary so the end date is January. Dataset for January id className startdate enddate 1 A 01/01/2019 1 B 01/01/2019 2 A 01/01/2019 3 B 01/01/2019 Dataset for February id className startdate enddate 1 A 01/02/2019 2 A 01/02/2019 3 B 01/02/2019 Dataset for march id schoolName startdate enddate 1 A 01/03/2019 1 B 01/03/2019 3 B 01/03/2019 Data Want id className startdate enddate 1 A 01/01/2019 1 B 01/01/2019 01/01/2019 1 A 01/02/2019 1 A 01/03/2019 1 B 01/03/2019 2 A 01/01/2019 2 A 01/02/2019 01/02/2019 3 B 01/01/2019 3 B 01/02/2019 3 B 01/03/2019
... View more