CREATE TABLE stocks(timestamp INT, price INT)

INSERT INTO stocks VALUES(1,15)
INSERT INTO stocks VALUES(2,19)
INSERT INTO stocks VALUES(3,16)
INSERT INTO stocks VALUES(4,17)
INSERT INTO stocks VALUES(5,15)
INSERT INTO stocks VALUES(6,13)
INSERT INTO stocks VALUES(7,5)
INSERT INTO stocks VALUES(8,8)
INSERT INTO stocks VALUES(9,7)
INSERT INTO stocks VALUES(10,13)
INSERT INTO stocks VALUES(11,11)
INSERT INTO stocks VALUES(12,14)
INSERT INTO stocks VALUES(13,10)
INSERT INTO stocks VALUES(14,5)
INSERT INTO stocks VALUES(15,2)
INSERT INTO stocks VALUES(16,5)

SELECT max(price-mins(price))
FROM stocks
     ASSUMING ASC timestamp