Question: What is the difference between the units sold for item 1 when the sunset was the earliest and the latest?
SQL: SELECT ( SELECT SUM(T2.units) AS sumunit FROM weather AS T1 INNER JOIN sales_in_weather AS T2 ON T1.`date` = T2.`date` INNER JOIN relation AS T3 ON T2.store_nbr = T3.store_nbr WHERE T2.item_nbr = 5 AND sunset IS NOT NULL GROUP BY T1.sunset ORDER BY T1.sunset LIMIT 1 ) - ( SELECT SUM(T2.units) AS sumunit FROM weather AS T1 INNER JOIN sales_in_weather AS T2 ON T1.`date` = T2.`date` INNER JOIN relation AS T3 ON T2.store_nbr = T3.store_nbr WHERE T2.item_nbr = 5 AND sunset IS NOT NULL GROUP BY T1.sunset ORDER BY T1.sunset DESC LIMIT 1 )