SUBQUERY
SELECT P.PRODUCT_CODE, (OS.SA * P.PRICE) AS 'SALES'
FROM (SELECT PRODUCT_ID, SUM(SALES_AMOUNT) AS SA
FROM OFFLINE_SALE
GROUP BY PRODUCT_ID) OS INNER JOIN PRODUCT P
USING(PRODUCT_ID)
ORDER BY SALES DESC, PRODUCT_CODEJOIN
SELECT P.PRODUCT_CODE, (P.PRICE * SUM(O.SALES_AMOUNT)) AS SALES
FROM PRODUCT P
JOIN OFFLINE_SALE O
ON P.PRODUCT_ID = O.PRODUCT_ID
GROUP BY P.PRODUCT_ID
ORDER BY SALES DESC, PRODUCT_CODE ASC