Database: sales_in_weather
Question: State the max temperature of the weather station which has the no.21 store on 2012/11/9.
SQL: SELECT tmax FROM weather AS T1 INNER JOIN relation AS T2 ON T1.station_nbr = T2.station_nbr WHERE T2.store_nbr = 21 AND T1.`date` = '2012-11-09'