T-SQL : merge insert old and new value then make changes - sql-server

Question

It's my first time working with T-SQL Merge and I have been trying to write a Stored Procedure using with the following condition:
If record is present then insert into Changes table the Id, old value (before update) and the new value and after that update the old value from Affected
if record is not present then insert into Changes the Id, empty for old and the new value and after that insert new record in Affected
if record didn't match then insert into Changes the Id, old value (value before deletion) and empty as new value and after that delete the record
Here are the tables I used
CREATE TABLE Affected
(
[Id] int IDENTITY(1,1) NOT NULL,
[ZoneId] int NOT NULL,
[Name] varchar(100) NOT NULL,
[Value] varchar(100)
)
CREATE TABLE Changes
(
[AffectedId] int NOT NULL,
[OldValue] varchar(100),
[NewValue] varchar(100)
)
And here is my stored procedure which takes two zone ids as input parameters
CREATE PROCEDURE spAffectChanges
#ZoneId1 int,
#ZoneId2 int
AS
IF(#ZoneId1 < 10)
BEGIN
;WITH fromQ AS
(
SELECT DISTINCT Name, Value
FROM Affected
WHERE ZoneId = #ZoneId1 AND Name NOT IN ('aaa', 'bbb', 'ccc')
), toQ AS
(
SELECT DISTINCT Name, Value
FROM Affected
WHERE ZoneId = #ZoneId2 AND Name NOT IN ('aaa', 'bbb', 'ccc')
)
MERGE toQ
USING fromQ ON (toQ.Name = fromQ.Name)
WHEN MATCHED AND fromQ.Value<>toQ.Value THEN
----first insert
INSERT INTO Changes (AffectedId, OldValue, NewValue)
VALUES(toQ.Id, toQ.Value, fromQ.Value)
----then update
UPDATE SET toQ.Value=fromQ.Value
WHEN NOT MATCHED BY toQ THEN
----first insert
INSERT INTO Changes (AffectedId, OldValue, NewValue)
VALUES(toQ.Id, '', fromQ.Value)
----second insert
INSERT (Name, Zone, Value)
VALUES (fromQ.Name, #ZoneId1, fromQ.Value)
WHEN NOT MATCHED BY fromQ THEN
----first insert
INSERT INTO Changes (AffectedId, OldValue, NewValue)
VALUES(toQ.Id, toQ.Value, '')
----then delete
DELETE
END
Is there a way to perform both insert to Changes and Update/Insert/Delete for Affected?
Thanks in advance

Answer 1

You can use the OUTPUT clause to do this.
Notes:
MERGE requires a semi-colon terminator. ;WITH is silly, ; is not a beginning-ator, it is meant to be placed at the end of every command
The options for WHEN NOT MATCHED are BY SOURCE and BY TARGET (this is the default)
I don't quite understand how you have a DISTINCT on the target, I don't believe it is allowed, nor how it makes sense to do so.
WITH fromQ AS
(
SELECT DISTINCT Name, Value
FROM Affected
WHERE ZoneId = #ZoneId1 AND Name NOT IN ('aaa', 'bbb', 'ccc')
), toQ AS
(
SELECT Name, Value
FROM Affected
WHERE ZoneId = #ZoneId2 AND Name NOT IN ('aaa', 'bbb', 'ccc')
)
MERGE toQ
USING fromQ ON (toQ.Name = fromQ.Name)
WHEN MATCHED AND fromQ.Value <> toQ.Value THEN
UPDATE
SET toQ.Value = fromQ.Value
WHEN NOT MATCHED BY TARGET THEN
INSERT (Name, Zone, Value)
VALUES (fromQ.Name, #ZoneId1, fromQ.Value)
WHEN NOT MATCHED BY SOURCE THEN
DELETE
OUTPUT inserted.Id, ISNULL(deleted.Value, ''), ISNULL(inserted.Value, '')
INTO Changes (AffectedId, OldValue, NewValue)
;