use NorthWind
SELECT
p1.unitprice, p1.productname,
COUNT(*) AS ranking -- 순위 만드는 쿼리
FROM
products p1, products p2
WHERE p1.categoryid = p2.categoryid
AND p1.categoryid = 4
AND p1.unitprice < p2.unitprice
GROUP BY
p1.unitprice , p1.productname
ORDER BY ranking ASC