sql merge question - updating not matched by source - sql-server

Question

I have a stored procedure that mergers Local temp table and existing table.
ALTER PROCEDURE [dbo].[SyncProductVariantsFromServices]
#Items ProductVariantsTable readonly
AS
BEGIN
CREATE TABLE #ProductVariantsTemp
(
ItemCode nvarchar(10) collate SQL_Latin1_General_CP1_CI_AS,
VariantCode nvarchar(10) collate SQL_Latin1_General_CP1_CI_AS,
VariantDescriptionBG nvarchar(100) collate SQL_Latin1_General_CP1_CI_AS,
VariantDescriptionEN nvarchar(100) collate SQL_Latin1_General_CP1_CI_AS
)
insert into #ProductVariantsTemp
select ItemCode, VariantCode, VariantDescriptionBG, VariantDescriptionEN
from #Items
MERGE ProductVariants AS TARGET
USING #ProductVariantsTemp AS SOURCE
ON (TARGET.ItemCode = SOURCE.ItemCode AND TARGET.VariantCode= SOURCE.VariantCode)
WHEN NOT MATCHED BY TARGET THEN
INSERT (ItemCode, VariantCode, VariantDescriptionBG, VariantDescriptionEN)
VALUES (SOURCE.ItemCode, SOURCE.VariantCode, SOURCE.VariantDescriptionBG, SOURCE.VariantDescriptionEN)
OUTPUT INSERTED.ItemCode, INSERTED.VariantCode, GETDATE() INTO SyncLog;
The problem is - i know in the output clause i have access to inserted or deleted records in case of Not merged by source. But in case 'not merged by source' I want to update
Update ProductVariants Set Active = 0
// when not matched by source
What is the most efficient way to do this?

Answer 1

Necessarily use `WHEN NOT MATCHED BY SOURCE 'when you want to delete a record that is not in the target table. if you want to 'inactivate' a record this must necessarily be done when the clause 'MATCHED' adding exceptions.
If you want to keep history of the records evaluate using "Slowly Changing Dimensions", I leave you some examples that Kimball uses for this treatment of historical data.
Slowly Changing Dimensions - Part 1
Slowly Changing Dimensions - Part 2

Answer 2

Use the WHEN NOT MATCHED BY SOURCE clause of the MERGE with an UPDATE statement.
MERGE
ProductVariants AS TARGET
USING
#ProductVariantsTemp AS SOURCE ON (TARGET.ItemCode = SOURCE.ItemCode AND TARGET.VariantCode= SOURCE.VariantCode)
WHEN
NOT MATCHED BY TARGET THEN
INSERT (ItemCode, VariantCode, VariantDescriptionBG, VariantDescriptionEN)
VALUES (SOURCE.ItemCode, SOURCE.VariantCode, SOURCE.VariantDescriptionBG, SOURCE.VariantDescriptionEN)
WHEN
NOT MATCHED BY SOURCE THEN
UPDATE SET Active = 0
OUTPUT
INSERTED.ItemCode, INSERTED.VariantCode, GETDATE() INTO SyncLog;
Since the OUTPUT clause for the INSERTED table might return either inserted or updated records now, you can add the special column $action that will tell you the original operation as INSERT or UPDATE. Will have to change the SyncLog table to recieve this value though.
OUTPUT
INSERTED.ItemCode, INSERTED.VariantCode, GETDATE(), $action
INTO SyncLog;