How many units of item 7 have been sold by store 7 when the snow is less than 5 inches?
item 7 refers to item_nbr = 7; store 7 refers to store_nbr = 7; snow is less than 5 inches refers to snowfall < 5
SELECT SUM(units) FROM weather AS T1 INNER JOIN relation AS T2 ON T1.station_nbr = T2.station_nbr INNER JOIN sales_in_weather AS T3 ON T2.store_nbr = T3.store_nbr WHERE T2.store_nbr = 7 AND T3.item_nbr = 7 AND T1.snowfall < 5
database name:db_id sales_in_weather
sales_in_weather table sales_in_weather Cols: date dtype date, store number dtype integer, item number dtype integer, units dtype integer, 
weather table weather Cols: station number dtype integer, date dtype date, temperature max dtype integer, temperature min dtype integer, temperature average dtype integer, departure from normal dtype integer, dew point dtype integer, wet bulb dtype integer, heat dtype integer, cool dtype integer, sunrise dtype text, sunset dtype text, code summarization dtype text, snowfall dtype real, preciptotal dtype real, station pressure dtype real, sea level dtype real, resultant speed dtype real, resultant direction dtype integer, average speed dtype real, 
relation table relation Cols: store number dtype integer, station number dtype integer, 
