SQL update trigger only when column is modified

By looking at other examples I've come up with the following but it doesn't seem to work as I would like: I want it to only update the modified information if the QtyToRepair value has been updated... but it doesn't do that.

If I comment out the where then the modified information is updated in every case. As I said other examples led me to be optimistic. Any clues appreciated. Thanks.

Walter

ALTER TRIGGER [dbo].[tr_SCHEDULE_Modified]
   ON [dbo].[SCHEDULE]
   AFTER UPDATE
AS 
BEGIN
	SET NOCOUNT ON;

    UPDATE SCHEDULE	SET modified = GETDATE()
	    , ModifiedUser = SUSER_NAME()
		, ModifiedHost = HOST_NAME()
    FROM SCHEDULE S
	INNER JOIN Inserted I on S.OrderNo = I.OrderNo and S.PartNumber = I.PartNumber
	WHERE S.QtyToRepair <> I.QtyToRepair
END

You have two way for your question :

1- Use Update Command in your Trigger.

ALTER TRIGGER [dbo].[tr_SCHEDULE_Modified]
   ON [dbo].[SCHEDULE]
   AFTER UPDATE
AS BEGIN
    SET NOCOUNT ON;
    IF UPDATE (QtyToRepair) 
    BEGIN
        UPDATE SCHEDULE 
        SET modified = GETDATE()
           , ModifiedUser = SUSER_NAME()
           , ModifiedHost = HOST_NAME()
        FROM SCHEDULE S INNER JOIN Inserted I 
        ON S.OrderNo = I.OrderNo and S.PartNumber = I.PartNumber
        WHERE S.QtyToRepair <> I.QtyToRepair
    END 
END

2- Use Join between Inserted table and deleted table

ALTER TRIGGER [dbo].[tr_SCHEDULE_Modified]
   ON [dbo].[SCHEDULE]
   AFTER UPDATE
AS BEGIN
    SET NOCOUNT ON;    

    UPDATE SCHEDULE 
    SET modified = GETDATE()
       , ModifiedUser = SUSER_NAME()
       , ModifiedHost = HOST_NAME()
    FROM SCHEDULE S 
    INNER JOIN Inserted I ON S.OrderNo = I.OrderNo and S.PartNumber = I.PartNumber
    INNER JOIN Deleted D ON S.OrderNo = D.OrderNo and S.PartNumber = D.PartNumber                  
    WHERE S.QtyToRepair <> I.QtyToRepair
    AND D.QtyToRepair <> I.QtyToRepair
END

When you use update command for table SCHEDULE and Set QtyToRepair Column to new value, if new value equal to old value in one or multi row, solution 1 update all updated row in Schedule table but solution 2 update only schedule rows that old value not equal to new value.

fyi The code I ended up with:

IF UPDATE (QtyToRepair)
    begin
        INSERT INTO tmpQtyToRepairChanges (OrderNo, PartNumber, ModifiedDate, ModifiedUser, ModifiedHost, QtyToRepairOld, QtyToRepairNew)
        SELECT S.OrderNo, S.PartNumber, GETDATE(), SUSER_NAME(), HOST_NAME(), D.QtyToRepair, I.QtyToRepair FROM SCHEDULE S
        INNER JOIN Inserted I ON S.OrderNo = I.OrderNo and S.PartNumber = I.PartNumber
        INNER JOIN Deleted D ON S.OrderNo = D.OrderNo and S.PartNumber = D.PartNumber 
        WHERE I.QtyToRepair <> D.QtyToRepair
end

One should check if QtyToRepair is updated at first.

ALTER TRIGGER [dbo].[tr_SCHEDULE_Modified]
   ON [dbo].[SCHEDULE]
   AFTER UPDATE
AS 
BEGIN
SET NOCOUNT ON;
    IF UPDATE (QtyToRepair) 
    BEGIN
        UPDATE SCHEDULE 
        SET modified = GETDATE()
           , ModifiedUser = SUSER_NAME()
           , ModifiedHost = HOST_NAME()
        FROM SCHEDULE S INNER JOIN Inserted I 
            ON S.OrderNo = I.OrderNo and S.PartNumber =    I.PartNumber
        WHERE S.QtyToRepair <> I.QtyToRepair
    END
END

You want to do the following:

ALTER TRIGGER [dbo].[tr_SCHEDULE_Modified]
   ON [dbo].[SCHEDULE]
   AFTER UPDATE
AS 
BEGIN
SET NOCOUNT ON;

    IF (UPDATE(QtyToRepair))
    BEGIN
	    UPDATE SCHEDULE	SET modified = GETDATE()
        	, ModifiedUser = SUSER_NAME()
	        , ModifiedHost = HOST_NAME()
        FROM SCHEDULE S
        INNER JOIN Inserted I ON S.OrderNo = I.OrderNo AND S.PartNumber = I.PartNumber
   	    WHERE S.QtyToRepair <> I.QtyToRepair
    END
END

Please note that this trigger will fire each time you update the column no matter if the value is the same or not.

Whenever a record has updated a record is "deleted". Here is my example:

ALTER TRIGGER [dbo].[UpdatePhyDate]
   ON  [dbo].[M_ContractDT1]
   AFTER UPDATE
AS 
BEGIN
	-- on ContarctDT1 PhyQty is updated 
	-- I want system date in Phytate automatically saved
	SET NOCOUNT ON;
	
	declare @dt1ky as int	
	
	if(update(Phyqty))
	begin
		select @dt1ky = dt1ky from deleted
		
		update M_ContractDT1 set PhyDate=GETDATE() where Dt1Ky=  @dt1ky		
	
	end

END

---

It works fine