SQL Count unique data by using count() and DISTINCT

Query the difference between all cities and all unique cities from the STATION table. This is the solution of HackerRank's Weather Observation Station 4 SQL problem.

Table name: STATION

Table Structure:

Fileds	Type
ID	NUMBER
CITY	VARCHAR
STATE	VARCHAR
LAT_N	NUMBER
LONG_W	NUMBER

 

SQL Query:

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