--
-- ec_order_gift_cert_amount/1
--
create or replace function ec_order_gift_cert_amount(
  integer
) returns numeric as $$

DECLARE
	v_order_id		alias for $1;
        gift_cert_amount        numeric;
BEGIN
        select into gift_cert_amount
        coalesce(sum(amount_used),0) - coalesce(sum(amount_reinstated),0)
        FROM ec_gift_certificate_usage
        WHERE order_id=v_order_id;

        return gift_cert_amount;
END;$$ language plpgsql;