Merge and Trigger - Primary Key Violation
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21-06-2021 - |
Question
I have those tables
CREATE TABLE [Test](
[Id] [int] NOT NULL,
[Value] [int] NOT NULL,
[Id_Test_2] [int] NOT NULL,
CONSTRAINT [PK_Test] PRIMARY KEY CLUSTERED
(
[Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
CREATE TABLE [Test_2](
[Id_Test_2] [int] NOT NULL,
[Value_Test_2] [int] NOT NULL,
CONSTRAINT [PK_Test_2] PRIMARY KEY CLUSTERED
(
[Id_Test_2] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
On the table Test i have an this update trigger:
CREATE TRIGGER [dbo].[Test_TriggerUpdate]
ON [dbo].[Test]
FOR UPDATE
NOT FOR REPLICATION
AS
BEGIN
MERGE Test_2 AS Target
USING
( SELECT D.Id_Test_2 ,
( COALESCE(D.Value, 0) * 2 ) AS Value
FROM Deleted D
) AS Source
ON ( Target.Id_Test_2 = Source.Id_Test_2 )
WHEN MATCHED
THEN
UPDATE
SET TARGET.Value_Test_2 = ( TARGET.Value_Test_2 - Source.Value )
WHEN NOT MATCHED BY TARGET
THEN
INSERT (
Id_Test_2 ,
Value_Test_2
)
VALUES ( Source.Id_Test_2 ,
(Source.[Value]*(-1))
);
MERGE Test_2 AS Target
USING
( SELECT I.Id_Test_2 ,
( COALESCE(I.Value, 0)
* 2 ) AS Value
FROM INSERTED I
) AS Source
ON ( Target.Id_Test_2 = Source.Id_Test_2
)
WHEN MATCHED
THEN
UPDATE
SET TARGET.Value_Test_2 = ( TARGET.Value_Test_2 + Source.Value )
WHEN NOT MATCHED BY TARGET
THEN
INSERT (
Id_Test_2 ,
Value_Test_2
)
VALUES ( Source.Id_Test_2 ,
Source.[Value]
);
END
table test_2 is empty and test have this record
Id Value Id_Test_2
1 10 1
2 20 1
3 30 2
when i run this update
UPDATE Test SET VALUE= 50
i have this kind of error
Msg 2627, Level 14, State 1, Procedure Test_TriggerUpdate, Line 12 Violation PRIMARY KEY 'PK_Test_2'. Impossible to insert duplicate key with value (1) into 'Test_2'.
Maybe this happen when Merge Operation is called with multirows and instead of call before INSERT and next UPDATE operation, it run two INSERT for record 1 and 2. What is possible to do?
La solution
Easy way to solve this problem is use a instruction of group by on the key and an aggregation function on values to sum as this:
ALTER TRIGGER [dbo].[Test_TriggerUpdate]
ON [dbo].[Test]
FOR UPDATE
NOT FOR REPLICATION
AS
BEGIN
MERGE Test_2 AS Target
USING
( SELECT D.Id_Test_2 ,
sum(( COALESCE(D.Value, 0) * 2 )) AS Value
FROM Deleted D
GROUP BY Id_Test_2
) AS Source
ON ( Target.Id_Test_2 = Source.Id_Test_2 )
WHEN MATCHED
THEN
UPDATE
SET TARGET.Value_Test_2 = ( TARGET.Value_Test_2 - Source.Value )
WHEN NOT MATCHED BY TARGET
THEN
INSERT ( Id_Test_2 ,
Value_Test_2
)
VALUES ( Source.Id_Test_2 ,
(Source.[Value]*(-1))
);
MERGE Test_2 AS Target
USING
( SELECT I.Id_Test_2 ,
sum(( COALESCE(I.Value, 0) * 2 )) AS Value
FROM INSERTED I
GROUP BY Id_Test_2
) AS Source
ON ( Target.Id_Test_2 = Source.Id_Test_2 )
WHEN MATCHED
THEN
UPDATE
SET TARGET.Value_Test_2 = ( TARGET.Value_Test_2 + Source.Value )
WHEN NOT MATCHED BY TARGET
THEN
INSERT ( Id_Test_2 ,
Value_Test_2
)
VALUES ( Source.Id_Test_2 ,
Source.[Value]
);
END
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