Data Warehouse Example?

hi, Can anyone list the type of error that will make @@error =1
I created a procedure to update a table based on a cutomer id, Id 7 doest not exist in table A, and I am suppose to have Not valid id, but in this case nothing happen I always get table a updated
thanks
Ali


begin tran
update table a
set title =' manager '
where id =7

if (@error <> 0)
begin
rollback tran
print 'not valid id '
return
end
ELSE
begin
commit tran
print 'table A updated'
end