How many more units of item no.16 were sold on the day with the highest max temperature in 2012 in store no.5 than in store no.10?
store no. 5 refers to store_nbr = 5; store no. 10 refers to store_nbr = 10; item no.16 refers to item_nbr = 16; in 2012 refers to SUBSTR(date, 1, 4) = '2012'; highest max temperature refers to Max(tmax); more units sold refers to Subtract ( Sum(units where store_nbr = 5), Sum(units where store_nbr = 10))
SELECT ( SELECT SUM(units) FROM sales_in_weather AS T1 INNER JOIN relation AS T2 ON T1.store_nbr = T2.store_nbr INNER JOIN weather AS T3 ON T2.station_nbr = T3.station_nbr WHERE T1.item_nbr = 16 AND T1.`date` LIKE '%2012%' AND T1.store_nbr = 5 GROUP BY tmax ORDER BY T3.tmax DESC LIMIT 1 ) - ( SELECT SUM(units) FROM sales_in_weather AS T1 INNER JOIN relation AS T2 ON T1.store_nbr = T2.store_nbr INNER JOIN weather AS T3 ON T2.station_nbr = T3.station_nbr WHERE T1.item_nbr = 16 AND T1.`date` LIKE '%2012%' AND T1.store_nbr = 6 GROUP BY tmax ORDER BY T3.tmax DESC LIMIT 1 )