Weather Observation Station 4~6 : hackerRank

Weather Observation Station 4

SELECT count(CITY) - count(DISTINCT CITY)
FROM STATION;

Weather Observation Station 5

SELECT CITY, length(CITY)
FROM STATION
WHERE CITY in (
    (SELECT  CITY
    FROM STATION
    WHERE length(CITY) = (SELECT MIN(length(CITY)) FROM STATION)
    ORDER BY CITY ASC
    LIMIT 0, 1),
    (SELECT  CITY
    FROM STATION
    WHERE length(CITY) = (SELECT MAX(length(CITY)) FROM STATION)
    ORDER BY CITY ASC
    LIMIT 0, 1)
);

Weather Observation Station 6

SELECT  DISTINCT  CITY
FROM    STATION
WHERE   UPPER(LEFT(CITY, 1)) IN ('A', 'E', 'I', 'O', 'U');