How many units of item no.5 were sold in store no.3 on the day the temperature range was the biggest?
item no. 5 refers to item_nbr = 5; store no.3 refers to store_nbr = 3; when the temperature range was the biggest refers to Max(Subtract(tmax, tmin))
SELECT t2.units FROM relation AS T1 INNER JOIN sales_in_weather AS T2 ON T1.store_nbr = T2.store_nbr INNER JOIN weather AS T3 ON T1.station_nbr = T3.station_nbr WHERE T2.store_nbr = 3 AND T2.item_nbr = 5 ORDER BY t3.tmax - t3.tmin DESC LIMIT 1