[HACKERRANK] Weather Observation Station 4

Q. 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:

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 

TOTOAL NUMBER RECORD - UMBER OF UNIQUE CITY NAMES = 3 - 2 = 1.

 

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

👉 COUNT - COUNT 연산은 처음 본 것 같아서 기록!!