SQL AFTER INSERT,UPDATE Trigger with condition if update specific column - sql-server

Question

I would like to create a trigger that inserts new datasets into the FREE08 table (see example code) either after insert on FREE03. This part works. But i also want to insert new dataset into FREE08 only if specific column (FK2) of FREE03 is updated. Thought this works with the "IF UPDATE(FK2) statement in the trigger.
What happens is i got a new dataset in FREE08 everytime i have any update in FREE03.
How can i get that?
Thanks for your support
USE [DB]
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TRIGGER [dbo].[Einsatzhistorie Wechsler]
ON [dbo].[FREE03]
AFTER INSERT,UPDATE
AS
SET NOCOUNT ON;
IF UPDATE(FK2)
BEGIN
INSERT INTO FREE08
(
FK1,FK2,TEXT3,DATE1,TEXT2,DATE4
)
Select FK2,FK1,ID,DATE1,TEXT1,DATE11 From inserted
end

Answer 1

I've never found a real use for the UPDATE function, since it tells you whether a column was subject to UPDATE (I.e. appeared in the SET clause), not whether data actually changed. In addition, of course, triggers fire once per statement, not once per row, so your trigger may be dealing with a mixture of rows, some of which had their FK2 changed and some not.
It's usually better to use deleted and compare the previous/current values:
CREATE TRIGGER [dbo].[Einsatzhistorie Wechsler]
ON [dbo].[FREE03]
AFTER INSERT,UPDATE
AS
SET NOCOUNT ON;
INSERT INTO FREE08
(
FK1,FK2,TEXT3,DATE1,TEXT2,DATE4
)
Select i.FK2,i.FK1,i.ID,i.DATE1,i.TEXT1,i.DATE11
From inserted i
left join deleted d
on
i.ID = d.ID and
i.FK2 = d.FK2
where d.ID is null
Here I've assumed a) that ID represents an immutable primary key for the table and b) That FK2 isn't nullable.