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풀이 STATION 테이블의 전체 CITY 항목에서 고유한 CITY의 갯수를 제외한 값을 출력해야 한다.소스코드보기출처 Weather Observation Station 4 | HackerRankFind the number of duplicate CITY names in STATION.www.hackerrank.com

문제Pascal University, one of the oldest in the country, needs to renovate its Library Building, because after all these centuries the building started to show the effects of supporting the weight of the enormous amount of books it houses.To help in the renovation, the Alumni Association of the University decided to organize a series of fund-raising dinners, for which all alumni were invited. Thes..

풀이STATION테이블에서 ID가 짝수인 행에 대해 CITY를 출력하면 된다.중복된 CITY가 없도록 해야 하므로 결과에 DISTINCT를 붙여주자.소스코드보기출처 Weather Observation Station 3 | HackerRankQuery a list of unique CITY names with even ID numbers.www.hackerrank.com

문제John and Mary have been friends since nursery school. Since then, they have shared a playful routine: every time they meet, they play Head or Tail with a coin, and whoever wins has the privilege of deciding what they are going to play during the day. Mary always choose Head, and John always choose Tail.Nowadays they are in college, but continue being truly good friends. Whenever they meet, the..