What was the average temperature difference between store number 18 and 19 on 16 September 2022?
store number 18 refers to store_nbr = 18; store number 19 refers to store_nbr = 19; on 16 September 2022 refers to date = '2022-09-16'; average temperature difference = Subtract(tavg where store_nbr = 18, tavg where store_nbr = 19)
SELECT SUM(CASE WHEN T1.store_nbr = 18 THEN T2.tavg ELSE 0 END) - SUM(CASE WHEN T1.store_nbr = 19 THEN T2.tavg ELSE 0 END) FROM relation AS T1 INNER JOIN weather AS T2 ON T1.station_nbr = T2.station_nbr WHERE T2.`date` = '2012-09-16'
CREATE TABLE sales_in_weather
(
    date      DATE,
    store_nbr INTEGER,
    item_nbr  INTEGER,
    units     INTEGER,
    primary key (store_nbr, date, item_nbr)
);
CREATE TABLE weather
(
    station_nbr INTEGER,
    date        DATE,
    tmax        INTEGER,
    tmin        INTEGER,
    tavg        INTEGER,
    depart      INTEGER,
    dewpoint    INTEGER,
    wetbulb     INTEGER,
    heat        INTEGER,
    cool        INTEGER,
    sunrise     TEXT,
    sunset      TEXT,
    codesum     TEXT,
    snowfall    REAL,
    preciptotal REAL,
    stnpressure REAL,
    sealevel    REAL,
    resultspeed REAL,
    resultdir   INTEGER,
    avgspeed    REAL,
    primary key (station_nbr, date)
);
CREATE TABLE relation
(
    store_nbr   INTEGER
            primary key,
    station_nbr INTEGER,
    foreign key (store_nbr) references sales_in_weather(store_nbr),
    foreign key (station_nbr) references weather(station_nbr)
);
