Derive Date Spans from Start and End Dates in SQL Server table

I am using SQL Server 2016 I have a table that contains 1 row per month that a patient is assigned to a particular Provider. A patient can be assigned to multiple providers during the year. How can I derive date spans (startdate & enddate) to represent the time a patient was assigned to each provider. My table looks like this: +----------+---------------+------------+-----------+ | Provider | Patient | StartDate | EndDate | +----------+---------------+------------+-----------+ | 1922157 | 12345 | 20191201 | 20191231 | | 1904176 | 12345 | 20191101 | 20191201 | | 1904176 | 12345 | 20191001 | 20191101 | | 1904176 | 12345 | 20190901 | 20191001 | | 1904176 | 12345 | 20190801 | 20190901 | | 1904176 | 12345 | 20190701 | 20190801 | | 1904176 | 12345 | 20190601 | 20190701 | | 1904176 | 12345 | 20190501 | 20190601 | | 1904176 | 12345 | 20190401 | 20190501 | | 1904176 | 12345 | 20190301 | 20190401 | | 1904176 | 12345 | 20190201 | 20190301 | | 1922157 | 12345 | 20190101 | 20190201 | | 1922157 | 56789 | 20190101 | 20190201 | +----------+---------------+------------+-----------+ In this case, patient 12345 was assigned to 2 different providers. One for 2 months, January and then December and the other for the rest of the year (10 months) February through November. Patient 56789 was only assigned to 1 provider (1922157) for 1 month (in December). I'm trying to make it so my output looks like the below table but I am running into issues I think because the patient is assigned to the same pcp during 2 different times of the year. I tried using the lag function but I only get the correct results for some cases but not all such as this particular case. +----------+---------------+------------+-----------+ | Provider | Patient | StartDate | EndDate | +----------+---------------+------------+-----------+ | 1922157 | 12345 | 20190101 | 20190201 | | 1904176 | 12345 | 20190201 | 20191201 | | 1922157 | 12345 | 20191201 | 20191231 | | 1922157 | 56789 | 20191201 | 20191231 | +----------+---------------+------------+-----------+ Update: Was doing some more research and came across the following post: https://stackoverflow.com/questions/35900765/ms-sql-combine-date-rows-into-start-end-date I just fit my table into the code in the answer for above question and tested for a few of my cases and it looks like it might get the job done. Unfortunately, my base table has 140k rows of dates it will need to calculate through so I am not sure how long it will take to run. Has been running now for 6 minutes, I will post back with results.