CREATE trigger tran_upd_trig after update on trans
REFERENCING old AS old_tran new AS new_tran
FOR EACH ROW
BEGIN
   If "old_tran"."tran_type" = 'R' Or
      "old_tran"."tran_type" = 'T' Then
      Update "product_master"
         Set "product_master"."product_balance" =
             "product_master"."product_balance" -
             "old_tran"."tran_qty" + "new_tran"."tran_qty"
         Where "product_master"."product_no" = 
               "old_tran"."tran_item_no"
   Elseif "old_tran"."tran_type" = 'I' Then
      Update "product_master"
         Set "product_master"."product_balance" =
             "product_master"."product_balance" +
             "old_tran"."tran_qty" - "new_tran"."tran_qty"
         Where "product_master"."product_no" = 
               "old_tran"."tran_item_no"
   End If
END;