-- Database schema
| sales_in_weather : date [ DATE ] , store_nbr [ INTEGER ] , item_nbr [ INTEGER ] , units [ INTEGER ] | weather : station_nbr [ INTEGER ] , date [ DATE ] , tmax [ INTEGER ] , tmin [ INTEGER ] , tavg [ INTEGER ] , depart [ INTEGER ] , dewpoint [ INTEGER ] , wetbulb [ INTEGER ] , heat [ INTEGER ] , cool [ INTEGER ] , sunrise [ TEXT ] , sunset [ TEXT ] , codesum [ TEXT ] , snowfall [ REAL ] , preciptotal [ REAL ] , stnpressure [ REAL ] , sealevel [ REAL ] , resultspeed [ REAL ] , resultdir [ INTEGER ] , avgspeed [ REAL ] | relation : store_nbr [ INTEGER ] primary_key relation.store_nbr = sales_in_weather.store_nbr , station_nbr [ INTEGER ] relation.station_nbr = weather.station_nbr |
-- -- Tell the temperature range of the home weather station of store no.7 on 2014/4/28.

SELECT T1.tmax - T1.tmin AS temprange FROM weather AS T1 INNER JOIN relation AS T2 ON T1.station_nbr = T2.station_nbr WHERE T2.store_nbr = 7 AND T1.`date` = '2014-04-28';