Trigger Which Make Rollback...

Hi,

I need help for this:
I need to make trigger which makes rollback
if INSERT- or UPDATE-statement try to make
dublicate row (col1+col2)
I try this, but it don't work:


CREATE TRIGGER trg_col1_col2_check
ON TABLE1
AFTER INSERT,UPDATE
AS
BEGIN
SET NOCOUNT ON
IF (SELECT DISTINCT 1
FROM TABLE1
GROUP BY col1, col2
HAVING count(*) > 1) = 1
BEGIN
IF (SELECT
case
when (i.col1 = ''
AND i.col2 = '') then 0
else 1
end
FROM INSERTED i) = 1
BEGIN
Print 'Col1 and col2 Already exist'
ROLLBACK
END
END
END