HackerRank: [SQL Aggregation] (12/17) Weather Observation Station-15 | round, max function in SQL

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.

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Recommended SQL Courses:

1. Udemy: SQL - MySQL for Data Analytics and Business Intelligence
2. LinkedIn: Master SQL for Data Science
3. edX: Databases: Advanced Topics in SQL
4. edureka: SQL Essentials Training & Certification
5. Coursera: Learn SQL Basics for Data Science
6. Eduonix: SQL Queries

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SQL Problem Statement:

Query the Western Longitude (LONG_W) for the largest Northern Latitude (LAT_N) in STATION that is less than 137.2345. Round your answer to 4 decimal places.

Input Format:

The STATION table is described as follows:

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

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Solution: Using ROUND & MAX Function (MySQL Query):

SELECT ROUND(LONG_W, 4)
FROM STATION
WHERE LAT_N = (SELECT MAX(LAT_N) FROM STATION WHERE LAT_N < 137.2345);

NOTE: 

1. ROUND Function is used to round the decimal numbers up to mentioned length after the decimal point. Here, 4 is passed because we want output scale up to 4 decimal points.
   Eg.
   ROUND(2.7685, 2) will return 2.77
   ROUND(2.3327, 0) will return 2.33
2. MAX is an aggregation function used to get the largest (maximum) value of all the records in the column name passed to the function.

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Expected Output:

117.2465

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-Akshay P Daga