CREATE CURSOR Sales (Customer I, Purchase D, Amount Y)
INSERT INTO Sales VALUES (1, {^2004/01/01}, 150)
INSERT INTO Sales VALUES (1, {^2004/01/02}, 200)
INSERT INTO Sales VALUES (1, {^2004/01/15}, 100)
INSERT INTO Sales VALUES (2, {^2004/02/05}, 50)
INSERT INTO Sales VALUES (3, {^2004/02/01}, 180)
INSERT INTO Sales VALUES (3, {^2004/01/01}, 100)

INSERT INTO Sales VALUES (1, {^2004/01/16}, 200)
INSERT INTO Sales VALUES (3, {^2004/01/02}, 100)

* all
SELECT Customer, Purchase, Amount ;
FROM Sales WHERE Amount = (SELECT MAX(Amount) FROM Sales S WHERE Customer = Sales.Customer)

* last
SELECT Customer, MAX(Purchase), Amount ;
FROM Sales WHERE Amount = (SELECT MAX(Amount) FROM Sales S WHERE Customer = Sales.Customer);
GROUP BY Customer, Amount