The best solution I've found to this type of issue is to create a date dimension table that shows various information for dates- in this case it could simply be date and month, but other implementations I've seen include whether or not a particular day is a holiday or a day in which employees will work.
Then, apply the date criteria to this dimension table and left join the results onto it-
CREATE TABLE date_dim (Date_eval, Month)
...
SELECT [t.DataPoint], [dd.Month]
FROM date_dim dd
LEFT JOIN Table t
ON t.[When] = dd.Date_Eval
WHERE
Date_eval >= DATEADD(MONTH, -7, @CurrentMonth)
Date_eval < @CurrentMonth
The downside of this approach is that you have to populate a table with data and that if you use a date dimension attribute that can change, such as whether or not employees work a certain day, the table is difficult to maintain automatically.
The upside is that you have a framework to build reports like this on, and one that can be reused as often as you need it.
Best Answer
I believe you cannot do that. But, I came across something similar answered on the forum already. You can achieve a similar effect by following the steps in the link below.
Please go through the below link and check if it might be useful to you.
https://stackoverflow.com/a/9503789/2818351
Credits to the original author who answered the question.