What was the temperature range of station no.1 on 2012/1/1?
on 2012/1/1 refers to date = '2012-01-01'; temperature range refers to Subtract (tmax, tmin); station no.1 refers to station_nbr = 1
SELECT tmax - tmin AS temrange FROM weather WHERE station_nbr = 1 AND `date` = '2012-01-01'