Weather Observation Station 4

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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 .

 

total number of records - number of unique city names = 3 - 2 = 1

 

번역 : STATION 테이블에서 CITY의 총 갯수에서 중복제거된 CITY의 갯수를 뺀 값은?

 

MSSQL

 

풀이 : 예를들면 STATION 테이블의 총 COUNT는 3이고 각각 값들이 KOREA, JAPAN, KOREA라면 중복제거된 CITY의 갯수는 2일 것임!

 

이런 계산은 처음해봐서 당황했다!

나의 첫 답은 SELECT COUNT(*) - COUNT(CITY) FROM STATION 이었는데

완전히 달랐음... 문제 이해를 잘 못했던 것 같음! 

 

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