T-SQL Merge statement in stored procedure throws error - sql-server

Question

Recently I have had to change a query from the following (fully working):
/****** WORKING ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [operations].[ROIWarehouseDatas]
(#Operation VARCHAR(50) = NULL,
#TableName NVARCHAR(255) = NULL,
#Results [dbo].[ForeSightData] READONLY)
AS
BEGIN
DECLARE #err INT
SET #err = 0
IF (#Operation = 'Insert')
BEGIN
DECLARE #SQLString NVARCHAR(4000)
DECLARE #ParamDefinition NVARCHAR(4000)
SET #SQLString = N'TRUNCATE TABLE ['+ #TableName + N'];
INSERT INTO ['+ #TableName + N']
SELECT [ID], [BrandName], [AdvertName], [VersionName], [WCPM]
FROM #Results;';
SET #ParamDefinition = N'#Operation VARCHAR(50), #Results [dbo].[ForeSightData] READONLY';
EXECUTE sp_executesql #SQLString, #ParamDefinition, #TableName, #Results
END
--ENDIF Insert
SET #err = ##ERROR
RETURN #err
END
To the following (not working):
/****** NOT WORKING ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [operations].[ROIWarehouseDatas]
(#Operation VARCHAR(50) = NULL,
#TableName NVARCHAR(255) = NULL,
#Results [dbo].[ForeSightData] READONLY)
AS
BEGIN
DECLARE #err INT
DECLARE #SQLString NVARCHAR(4000)
DECLARE #ParamDefinition NVARCHAR(4000)
SET #err = 0
IF (#Operation = 'Insert')
BEGIN
SET #SQLString = N'MERGE INTO ['+ #TableName +'] AS T
USING #Results AS S ON T.ID = S.ID
WHEN MATCHED
THEN UPDATE
SET T.[BrandName] = S.[BrandName],
T.[AdvertName] = S.[AdvertName],
T.[VersionName] = S.[VersionName],
T.[VersionDuration] = S.[VersionDuration],
T.[WCPM] = S.[WCPM]
WHEN NOT MATCHED BY TARGET
THEN INSERT ([ID], [BrandName], [AdvertName], [VersionName], [WCPM])
VALUES (S.[ID], S.[BrandName], S.[AdvertName], S.[VersionName], S.[WCPM]);';
SET #ParamDefinition = N'#Operation VARCHAR(50), #Results [dbo].[ForeSightData] READONLY';
EXECUTE sp_executesql #SQLString, #ParamDefinition, #TableName, #Results
END
--ENDIF Insert
SET #err = ##ERROR
RETURN #err
END
However, when I run the program I get the following error:
An object or column name is missing or empty. For SELECT INTO statements, verify each column has a name. For other statements, look for empty alias names. Aliases defined as "" or [] are not allowed. Change the alias to a valid name. Unclosed quotation mark after the character string ''.
Incorrect syntax near ''.
I tried checking the syntax - and that came up as fine.

Answer 1

Seems not correct syntax for SQL MERGE.
WHEN NOT MATCHED BY T THEN should be Target not T:
WHEN NOT MATCHED BY Target
THEN .....