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Editorial Team
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Asked: 2026-05-23T04:00:21+00:00

I created a trigger for a table (Person) so that each time a new

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I created a trigger for a table (Person) so that each time a new Person entry is created its ID is inserted in another table (Person_ID). Person_ID table has only 2 rows: ID (primary key, int and Identity) and Person_ID (GUID whose values is passed with the trigger).
This schema cannot be changed due to other dependencies with our business logic.

Now I need to update a field of Person table with the Person_ID.ID (the identity automatically generated once that person has been created). To do that I created a trigger for Person_ID so that once a new entry is created, the generated ID will updated the target field in Person table:

UPDATE Person
SET target_Person = (SELECT JPerson_ID.ID FROM inserted)
WHERE Person.ID IN (SELECT JPerson_ID.PersonID FROM inserted)

When I create a new Person I get the following exception:

Violation of PRIMARY KEY constraint 'TBL_PERSON_A_PK'. 
Cannot insert duplicate key in object 'dbo.TBL_PERSON_A.

There is an update trigger associated to table Person that comes from a legacy component and I cannot edit or see it (it is encrypted). It seems the reason of the exception above.

Why do I get this exception even if I simply make an UPDATE and not an insert?

To solve this I disable such a trigger before executing the update and then enabling it again and it works like a charm: 

EXECUTE sp_executesql N'DISABLE TRIGGER dbo.TBL_PERSON_TRU1 ON PERSON'
...
EXECUTE sp_executesql N'ENABLE TRIGGER dbo.TBL_PERSON_TRU1 ON PERSON'

However how can I be sure that this will not bring to logic errors?
Thanks.

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1 Answer

  1. Editorial Team

    I don’t know if this causes your problem, but have you kept in mind that your (SELECT JPerson_ID.ID FROM inserted) could return more than one row?

    So you insert trigger must be changed to somewhat like:

    CREATE TRIGGER [dbo].[trgJPerson_ID] ON [dbo].[TBL_PERSON_A]
FOR INSERT
AS

INSERT INTO dbo.JPerson_ID(ID )
    SELECT ID FROM inserted

    and accordingly the delete-trigger(if you have one)

    CREATE TRIGGER [dbo].[trgJPerson_ID] ON [dbo].[TBL_PERSON_A]
FOR DELETE
AS

DELETE FROM dbo.JPerson_ID
    WHERE ID IN(SELECT ID FROM DELETED)
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