Re: need help in building a query

Try:

bdteste=# SELECT o1.user_id, o1.order_id, '>= 500' AS cond FROM Orders o1
bdteste-#  WHERE (SELECT sum(o2.amount_paid) FROM Orders o2 WHERE
o2.user_id = o1.user_id AND o2.order_id > o1.order_id) < 500 AND
bdteste-#        (SELECT sum(o2.amount_paid) FROM Orders o2 WHERE
o2.user_id = o1.user_id AND o2.order_id >= o1.order_id) >=500
bdteste-# UNION
bdteste-# SELECT user_id, min(order_id) AS "min order id", '< 500' AS
cond FROM Orders
bdteste-#  WHERE user_id IN (SELECT user_id FROM Orders GROUP BY
user_id HAVING sum(amount_paid) < 500)
bdteste-#  GROUP BY user_id;
 user_id | order_id |  cond
---------+----------+--------
      1 |        2 | >= 500
      2 |        3 | < 500

Osvaldo