SESSION NAME: Advance Select - 1

QUESTION NAME: Weather Observation - Query 3


TABLE DESCRIPTION:
Let N be the number of CITY entries in STATION, and let 
N' be the number of distinct CITY names in STATION; 
query the value of N - N' from STATION. In other words,
find the difference between the total number of CITY 
entries in the table and the number of distinct CITY 
entries in the table.

CODE:
select COUNT(CITY)-COUNT(DISTINCT CITY) from STATION;