Show Monthly Revenue By EmployeeID
You could consider to use a PIVOT solution:


Declare @Monetary Table(empID varchar(10), empsaleamt float, empsaledate date)
Insert Into @Monetary (empID, empsaleamt, empsaledate) Values
('123abc', 100.00, '20160101'), 
('123abc', 200.00, '20160101'), 
('123abc', 300.00, '20160201'),
('456cde', 200.00, '20160101'), 
('456cde', 100.00, '20160201'), 
('456cde', 100.00, '20160301'),
('123abc', 100.00, '20170101'), 
('123abc', 200.00, '20170101'), 
('123abc', 300.00, '20170201'),
('456cde', 200.00, '20170101'), 
('456cde', 100.00, '20170201'), 
('456cde', 100.00, '20170301');

SELECT ID, [1],[2],[3],[4],[5],[6],[7],[8],[9],[10],[11],[12]
FROM 
    (SELECT CONCAT(empId,'-',CAST(YEAR(empsaledate) AS varchar(10))) as ID, 
            month(empsaledate) AS months, empsaleamt
     FROM   @monetary ) src
PIVOT 
    (SUM(empsaleamt) FOR months IN ([1],[2],[3],[4],[5],[6],[7],[8],[9],[10],[11],[12])) pvt;

GO


ID          |   1 |   2 |    3 |    4 |    5 |    6 |    7 |    8 |    9 |   10 |   11 |   12
:---------- | --: | --: | ---: | ---: | ---: | ---: | ---: | ---: | ---: | ---: | ---: | ---:
123abc-2016 | 300 | 300 | null | null | null | null | null | null | null | null | null | null
123abc-2017 | 300 | 300 | null | null | null | null | null | null | null | null | null | null
456cde-2016 | 200 | 100 |  100 | null | null | null | null | null | null | null | null | null
456cde-2017 | 200 | 100 |  100 | null | null | null | null | null | null | null | null | null


dbfiddle here