Among the subscriber, how many of them finished the 2nd at Folsom and Civic Center BART (7th at Market) as their start and end stations respectively for no more than 490 seconds under minimum visibility of 4 miles.
subscription_type = 'Subscriber'; no more than 490 seconds refers to duration<490; start_station_name = '2nd at Folsom'; end_station_name = 'Civic Center BART (7th at Market)'; min_visibility_miles = 4;
SELECT COUNT(T1.id) FROM trip AS T1 INNER JOIN weather AS T2 ON T2.zip_code = T1.zip_code WHERE T1.subscription_type = 'Subscriber' AND T2.min_visibility_miles = 4 AND T1.duration < 490 AND T1.start_station_name = '2nd at Folsom' AND T1.end_station_name = 'Civic Center BART (7th at Market)'
CREATE TABLE IF NOT EXISTS "station"
(
    id                INTEGER not null
        primary key,
    name              TEXT,
    lat               REAL,
    long              REAL,
    dock_count        INTEGER,
    city              TEXT,
    installation_date TEXT
);
CREATE TABLE IF NOT EXISTS "status"
(
    station_id      INTEGER,
    bikes_available INTEGER,
    docks_available INTEGER,
    time            TEXT
);
CREATE TABLE IF NOT EXISTS "trip"
(
    id                 INTEGER not null
        primary key,
    duration           INTEGER,
    start_date         TEXT,
    start_station_name TEXT,
    start_station_id   INTEGER,
    end_date           TEXT,
    end_station_name   TEXT,
    end_station_id     INTEGER,
    bike_id            INTEGER,
    subscription_type  TEXT,
    zip_code           INTEGER
);
CREATE TABLE IF NOT EXISTS "weather"
(
    date                           TEXT,
    max_temperature_f              INTEGER,
    mean_temperature_f             INTEGER,
    min_temperature_f              INTEGER,
    max_dew_point_f                INTEGER,
    mean_dew_point_f               INTEGER,
    min_dew_point_f                INTEGER,
    max_humidity                   INTEGER,
    mean_humidity                  INTEGER,
    min_humidity                   INTEGER,
    max_sea_level_pressure_inches  REAL,
    mean_sea_level_pressure_inches REAL,
    min_sea_level_pressure_inches  REAL,
    max_visibility_miles           INTEGER,
    mean_visibility_miles          INTEGER,
    min_visibility_miles           INTEGER,
    max_wind_Speed_mph             INTEGER,
    mean_wind_speed_mph            INTEGER,
    max_gust_speed_mph             INTEGER,
    precipitation_inches           TEXT,
    cloud_cover                    INTEGER,
    events                         TEXT,
    wind_dir_degrees               INTEGER,
    zip_code                       TEXT
);
