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HackerRank: [SQL Basic Select] (9/20) Weather Observation Station-4 | Difference between total & distinct cities counts

HackerRank: [Basic Select - 9/20] Weather Observation Station-4 | Difference between total & distinct cities counts
I started studying SQL from a very famous site - HackerRank. Here I will try to provide multiple approaches & solutions to the same problem. It will help you learn and understand SQL in a better way.

Please make use of my blog posts for learning purpose only and feel free to ask your questions in the comment box below in case of any doubt.

Click Here for the previous blog-post in the series.


SQL Problem Statement:

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:

Table: STATION
Table: STATION
where LAT_N is the northern latitude and LONG_W is the western longitude.





Sample data in Table (STATION):
ID CITY STATE LAT_N LONG_W
794 Kissee Mills MO 140 73
824 Loma Mar CA 49 131
603 Sandy Hook CT 72 148
478 Tipton IN 34 98
619 Arlington CO 75 93
711 Turner AR 50 101
839 Slidell LA 85 152
.
.
.
754 South Haven MI 145 53
144 Eskridge KS 1




Solution (MySQL Query):
SELECT (count(CITY) - count(DISTINCT CITY)) as DIFFERENCE
FROM STATION;

Sample Output:
13




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-Akshay P Daga

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