SQL Merge not inserting new row - sql

Question

I am trying to use T-SQL Merge to check for the existence of records and update, if not then insert.
The update works fine, but the insert is not working.
Any and all help on this would be gratefully received.
DECLARE
#OperatorID INT = 2,
#CurrentCalendarView VARCHAR(50) = 'month';
WITH CTE AS
(
SELECT *
FROM dbo.OperatorOption
WHERE OperatorID = #OperatorID
)
MERGE INTO OperatorOption AS T
USING CTE S ON T.OperatorID = S.OperatorID
WHEN MATCHED THEN
UPDATE
SET T.CurrentCalendarView = #CurrentCalendarView
WHEN NOT MATCHED BY TARGET THEN
INSERT (OperatorID, PrescriptionPrintingAccountID, CurrentCalendarView)
VALUES (#OperatorID, NULL, #CurrentCalendarView);

Answer 1

When would a row Selected from OperatorOption not already exist in OperatorOption?
If you're saying this code does not insert - you're right it doesn't because the row has to be there to begin with (in which case it won't insert), or the row is not there to begin with, in which case there is nothing in the source dataset to insert.
Does
SELECT *
FROM dbo.OperatorOption
WHERE OperatorID = #OperatorID
return anything or not?
This does not work the way you think it does. There is nothing in the source CTE.
The answer to 'was a blank dataset missing from the target' is 'No' so nothing is inserted
To do this operation, I use this construct:
INSERT INTO dbo.OperatorOption
(OperatorID, PrescriptionPrintingAccountID, CurrentCalendarView)
SELECT #OperatorID, NULL, #CurrentCalendarView
WHERE NOT EXISTS (
SELECT * FROM dbo.OperatorOption
WHERE OperatorID = #OperatorID
)

Answer 2

It does not matter you are inserting values as variables. It thinks there is nothing to insert.
You need to produce data that does not match.
Like this:
DECLARE #OperatorID INT = 3, #CurrentCalendarView VARCHAR(50) = 'month';
declare #t table (operatorID int, CurrentCalendarView varchar(50));
insert into #t values (2, 'year');
MERGE #t AS TARGET
USING (SELECT #OperatorID, #CurrentCalendarView) AS source (operatorID, CurrentCalendarView)
on (TARGET.operatorID = Source.operatorID)
WHEN MATCHED THEN
UPDATE SET TARGET.CurrentCalendarView = #CurrentCalendarView
WHEN NOT MATCHED BY TARGET THEN
INSERT (OperatorID, CurrentCalendarView)
VALUES (source.OperatorID, source.CurrentCalendarView);
select * from #t

Answer 3

Insert probably isn't working because your source CTE does not produce any rows. Depending on how your table is organised, you might need to select from some other source, or use table valued constructor to produce source data.