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Weather Observation Station 4 | HackerRank
Find the number of duplicate CITY names in STATION.
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Problem
Find the difference between the total number of CITY entries in the table and the number of distinct CITY entries in the table.
-> station에 있는 모든 city의 수와 중복을 제외한 city의 수의 차이를 구하시오.
Answer
select count(city) - count(distinct(city))
from station728x90
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