ALTER TRIGGER [dbo].[ArchiveBACK] ON [dbo].[RLFL]
   AFTER INSERT
AS
BEGIN
SET NOCOUNT ON;

	DECLARE @soNo varchar(10),@releaseDate smalldatetime

	SELECT @soNo = soNo FROM INSERTED
	SELECT @releaseDate=releaseDate FROM INSERTED


-- Check if BACK records were archived, if NOT...
IF(SELECT COUNT(1) FROM BACK_RLFL WHERE salesOrderNo=@soNo AND releaseDate=@releaseDate AND releaseVersion='1') = 0
	-- Archive BACK Records, with version 1
	INSERT INTO BACK_RLFL SELECT *, @releaseDate,'1' FROM BACK WHERE salesOrderNo=@soNo

END

We walk in the dark places no others will enter
We stand on the bridge and no one may pass

ALTER TRIGGER [dbo].[ArchiveBACK] ON [dbo].[RLFL]
AFTER INSERT
AS
SET NOCOUNT ON;

INSERT INTO BACK_RLFL 
SELECT * FROM INSERTED  
EXCEPT
SELECT * FROM BACK_RLFL

BACK Table:
OrderID        ItemNo
---------    ---------
9813           1
9813           2
9813           3
9817           1

INSERT INTO BACK_ARCHIVE SELECT * FROM BACK WHERE OrderID=INSERTED.OrderID

OrderId       ItemNo
---------   ----------
9813          3

We walk in the dark places no others will enter
We stand on the bridge and no one may pass

DECLARE @soNo varchar(10),@releaseDate smalldatetime

SELECT @soNo = soNo FROM INSERTED
SELECT @releaseDate=releaseDate FROM INSERTED

We walk in the dark places no others will enter
We stand on the bridge and no one may pass

create table RLFL (OrderID int, ItemNo int);
GO
create table BACK (OrderID int, ItemNo int);
GO
create table BACK_RLFL (OrderID int, ItemNo int);
GO
CREATE TRIGGER [dbo].[ArchiveBACK] ON [dbo].[RLFL]
   AFTER INSERT
AS
SET NOCOUNT ON;

INSERT INTO BACK_RLFL 
SELECT b.* 
FROM BACK b 
INNER JOIN INSERTED i on b.OrderID = i.OrderIDGO