Odtnhj

I've created below code to implement SCD type 2 using merge, when i run the code i'm getting primary key violations on csname field. I have the below values as part of primary key, not sure whether merge SQL does support for varchar or not.
if I run the normal inner join SQL on the same key then i'm getting the matching records as well.

Any help much appreciated

csname
ER - Building Complaints
TR - Building Applications

CREATE PROCEDURE dbo.load_target
AS

BEGIN 
 INSERT INTO [TR_DW].[enum].[Rt]([csname],[enddatetime],[EffectiveToDate],[EffectiveFromDate],[CurrentRecord])
 SELECT[csname],[enddatetime],[EffectiveToDate],[EffectiveFromDate],[CurrentRecord]
 FROM
 (

 MERGE [TR_DW].[enum].[Rt] RtCSQSuTT
 USING [TR].[enum].[Rt] RtCSQSuST
 ON (RtCSQSuTT.csname = RtCSQSuST.csname)

 WHEN NOT MATCHED THEN
 INSERT ([csname],[enddatetime],[EffectiveToDate],[EffectiveFromDate],[CurrentRecord])
 VALUES ([csname],[enddatetime],'12/31/9999', getdate(), 'Y')
 WHEN MATCHED AND RtCSQSuTT.[CurrentRecord] = 'Y' AND 
 (ISNULL(RtCSQSuTT.[enddatetime], '') != ISNULL(RtCSQSuST.[enddatetime], ''))THEN
 UPDATE SET 
 RtCSQSuTT.[CurrentRecord] = 'N', 
 RtCSQSuTT.[EffectiveFromDate] = GETDATE() - 1,
 RtCSQSuTT.[EffectiveToDate] = GETDATE() 
 OUTPUT $Action Action_Taken,RtCSQSuST.[csqname],RtCSQSuST.[enddatetime],'12/31/9999' AS[EffectiveToDate],GETDATE() AS[EffectiveFromDate],'Y' AS[CurrentRecord]
)AS MERGE_OUT21
WHERE MERGE_OUT21.Action_Taken = 'UPDATE';

END 
GO