T-SQL query to summarize sales for ALL YEARS: with total per month per year, and cumulative monthly amounts

I need to create a Sales Report that shows all years sales per month, and cumulative sales. The database table is simple:

Transactions 
(
    ID INT, 
    TransactionDate DATETIME, 
    SalesAmount MONEY
)

I want the results to look similar to ExcelSheet below (I am showing only 2017/2018 amounts, but actual query needs to return results for all available years according to TransactionDate)

Answer

Try it:

With Q 
as
(
   Select DatePart(yyyy,TransactionDate) 'Year',DatePart(m,TransactionDate) 'Month',  sum(SalesAmount) 'Sales'
   From Transactions 
   Group by DatePart(yyyy,TransactionDate),DatePart(m,TransactionDate)
) 
Select q.Year,q.Month,q.sales,( Select sum(q1.Sales)
        From Q q1
        Where q1.Year=q.Year
         And  q1.Month <= q.Month
        ) 'Cumulative Sale'
From Q q
Order by q.Year,q.Month