Group Records By Time Period - tsql

Question

I'm trying to take a time frame the user selects and then group the selection into time periods - in this case: 2 weeks.
For instance, today is 5/4/2018 and if I set that as my start date and 5/31/2018 as my end date, I get the following:
DECLARE #StartDate DATE ,
#EndDate DATE ,
#ToDate DATE;
SET #StartDate = GETDATE ();
SET #EndDate = '20180531';
SET #ToDate = DATEADD ( DAY, 1, #EndDate );
SELECT dd.Date ,
ROW_NUMBER () OVER ( ORDER BY DATEPART ( WEEK, dd.Date )) AS [rownumb]
FROM dbo.DateDimension AS [dd]
WHERE dd.Date >= #StartDate
AND dd.Date < #ToDate;
And the results look like:
Date rownumb
2018-05-04 1
2018-05-05 2
2018-05-06 3
2018-05-07 4
2018-05-08 5
2018-05-09 6
2018-05-10 7
2018-05-11 8
2018-05-12 9
2018-05-13 10
2018-05-14 11
2018-05-15 12
2018-05-16 13
2018-05-17 14
2018-05-18 15
2018-05-19 16
2018-05-20 17
2018-05-21 18
2018-05-22 19
2018-05-23 20
2018-05-24 21
2018-05-25 22
2018-05-26 23
2018-05-27 24
2018-05-28 25
2018-05-29 26
2018-05-30 27
2018-05-31 28
I was playing around with ROW_NUMBER ( along with RANK and DENSE_RANK ) but I have not been able to get these functions to accomplish what I am looking for but what I am hoping to do is have an additional column called "TimePeriod" where the dates are grouped together in 2-week increments ( or 14 days ) so that 5/4/18 through 5/17/18 have a value of 1 for the "TimePeriod" column and 5/18/18 through 5/31/18 would have a value of 2 for the "TimePeriod" column. And this should be dynamic so that wider date ranges are grouped in periods of two weeks with each period increasing by 1.
Suggestions?

Answer 1

If there's no requirement to use the ordering and ranking functions in sql, you can easily implement as below.
get the total number of days between the start and end date
for each date you subtract the days difference of the current date from the total days difference, then divide this by 14
so this basically will give you the interval (2 weeks) to which the current date belongs, it's zero based so you might want to add a 1 to it
DECLARE #StartDate DATE ,
#EndDate DATE ,
#ToDate DATE;
DECLARE #DaysDiff INT;
SET #StartDate = GETDATE ();
SET #EndDate = '20180531';
SET #ToDate = DATEADD ( DAY, 1, #EndDate );
--GET the difference in days between the start and end date
SET #DaysDiff = DATEDIFF( Day, #StartDate,#ToDate )
SELECT dd.Date ,
( #DaysDiff - DATEDIFF(Day,dd.Date,#ToDate) )/14
FROM dbo.DateDimension AS [dd]
WHERE dd.Date >= #StartDate
AND dd.Date < #ToDate;