### Database Schema:
CREATE TABLE relation (
	store_nbr	INTEGER	NULL	PRIMARY KEY,
	station_nbr	INTEGER	NULL,
	foreign key (store_nbr) references sales_in_weather (store_nbr),
	foreign key (station_nbr) references weather (station_nbr)
);

CREATE TABLE weather (
	station_nbr	INTEGER	NULL	PRIMARY KEY,
	date	DATE	NULL	PRIMARY KEY,
	tmax	INTEGER	NULL,
	tmin	INTEGER	NULL,
	tavg	INTEGER	NULL,
	depart	INTEGER	NULL,
	dewpoint	INTEGER	NULL,
	wetbulb	INTEGER	NULL,
	heat	INTEGER	NULL,
	cool	INTEGER	NULL,
	sunrise	TEXT	NULL,
	sunset	TEXT	NULL,
	codesum	TEXT	NULL,
	snowfall	REAL	NULL,
	preciptotal	REAL	NULL,
	stnpressure	REAL	NULL,
	sealevel	REAL	NULL,
	resultspeed	REAL	NULL,
	resultdir	INTEGER	NULL,
	avgspeed	REAL	NULL
);

CREATE TABLE sales_in_weather (
	date	DATE	NULL	PRIMARY KEY,
	store_nbr	INTEGER	NULL	PRIMARY KEY,
	item_nbr	INTEGER	NULL	PRIMARY KEY,
	units	INTEGER	NULL
);

### User's Query:
Which weather station does the store that sold the highest quantity of item 9 belongs to?

### Extra Knowledge:
item 9 refers to item_nbr = 9; sold the highest quantity refers to Max(Sum(units)); weather station refers to station_nbr
SELECT station_nbr FROM sales_in_weather AS T1 INNER JOIN relation AS T2 ON T1.store_nbr = T2.store_nbr WHERE T1.item_nbr = 9 GROUP BY T2.station_nbr ORDER BY SUM(T1.units) DESC LIMIT 1