-- -- 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;