Which items from store 1 have the highest units sold during rainy day?
store 1 refers to store_nbr = 1; highest unit sold refers to Max(units); during rainy day refers to codesum like '%'||'RA'||'%'; item refers to item_nbr
SELECT T2.item_nbr 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 AND T1.station_nbr = T3.station_nbr WHERE T2.store_nbr = 1 AND T1.codesum LIKE '%' OR 'RA' OR '%' GROUP BY T2.item_nbr ORDER BY T2.units DESC LIMIT 1