HackerRank: [SQL Basic Join] (1/8) ASIAN POPULATION | inner join 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.

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.

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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:

Given the CITY and COUNTRY tables, query the sum of the populations of all cities where the CONTINENT is 'Asia'.

Note: CITY.CountryCode and COUNTRY.Code are matching key columns.

Input Format:

The CITY and COUNTRY tables are described as follows:

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Solution: Using INNER JOIN OR JOIN (MySQL Query):

SELECT SUM(B.POPULATION)
FROM COUNTRY A
JOIN CITY B
ON A.CODE = B.COUNTRYCODE
WHERE A.CONTINENT = 'Asia';

NOTE: 

1. SUM is an aggregation function used to calculate the sum or total of the values of all the records in the column name passed to the function.
   
   
2. JOIN and INNER JOIN are the same in SQL. It returns the records that have matching values in both tables.

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Expected Output:

27028484

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-Akshay P Daga