[해커랭크] Weather Observation Station 4

문제링크 : https://www.hackerrank.com/challenges/weather-observation-station-4/problem?isFullScreen=true

 

❓문제

Find the difference between the total number of CITY entries in the table and the number of distinct CITY entries in the table.
The STATION table is described as follows:

where LAT_N is the northern latitude and LONG_W is the western longitude.
For example, if there are three records in the table with CITY values 'New York', 'New York', 'Bengalaru', there are 2 different city names: 'New York' and 'Bengalaru'. The query returns , because .

 

❗답

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

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🤔풀이

전체 CITY 개수에서 중복 CITY 개수 제거