Merge historical periods of an dimension entity into one - sql

Question

I have a Slowly Changing Dimension type 2 with rows that are identical (besides the Start and End date). How do I write a pretty SQL query to merge rows that identical and have connected time periods?
Current data
+-------------+---------------------+--------------+------------+
| DimensionID | DimensionAttribute | RowStartDate | RowEndDate |
+-------------+---------------------+--------------+------------+
| 1 | SomeValue | 2019-01-01 | 2019-01-31 |
| 1 | SomeValue | 2019-02-01 | 2019-02-28 |
| 1 | AnotherValue | 2019-03-01 | 2019-03-31 |
| 1 | SomeValue | 2019-04-01 | 2019-04-30 |
| 1 | SomeValue | 2019-05-01 | 2019-05-31 |
| 2 | SomethingElse | 2019-01-01 | 2019-01-31 |
| 2 | SomethingElse | 2019-02-01 | 2019-02-28 |
| 2 | SomethingElse | 2019-03-01 | 2019-03-31 |
| 2 | CompletelyDifferent | 2019-04-01 | 2019-04-30 |
| 2 | SomethingElse | 2019-05-01 | 2019-05-31 |
+-------------+---------------------+--------------+------------+
Result
+-------------+---------------------+--------------+------------+
| DimensionID | DimensionAttribute | RowStartDate | RowEndDate |
+-------------+---------------------+--------------+------------+
| 1 | SomeValue | 2019-01-01 | 2019-02-28 |
| 1 | AnotherValue | 2019-03-01 | 2019-03-31 |
| 1 | SomeValue | 2019-04-01 | 2019-05-31 |
| 2 | SomethingElse | 2019-01-01 | 2019-03-31 |
| 2 | CompletelyDifferent | 2019-04-01 | 2019-04-30 |
| 2 | SomethingElse | 2019-05-01 | 2019-05-31 |
+-------------+---------------------+--------------+------------+

Answer 1

For this version of the problem, I would use lag() to determine where the groups start, then a cumulative sum and aggregation:
select dimensionid, DimensionAttribute,
min(row_start_date), max(row_end_date)
from (select t.*,
sum(case when prev_red = dateadd(day, -1, row_start_date)
then 0 else 1
end) over (partition by dimensionid, DimensionAttribute order by row_start_date) as grp
from (select t.*,
lag(row_end_date) over (partition by dimensionid, DimensionAttribute order by row_start_date) as prev_red
from t
) t
) t
group by dimensionid, DimensionAttribute, grp;
In particular, this will recognize gaps in the rows. It will only combine rows when they exactly fit together -- the previous end date is one day before the start date. This can be tweaked, of course, to allow a gap of 1 or 2 days or to allow overlaps.