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HackerRank: [SQL Aggregation] (4/17) AVERAGE POPULATION | avg, floor & round function in SQL

HackerRank: [SQL Aggregation - 4/17] Average Population | AVG, FLOOR & ROUND 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.

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:

Query the average population for all cities in CITY, rounded down to the nearest integer.



Input Format:

The CITY table is described as follows:

CITY Columns




Solution-1: Using ROUND & AVG Function (MySQL Query):

SELECT ROUND(AVG(POPULATION), 0)
FROM CITY;

NOTE: 
  1. AVG is an aggregation function used to calculate the average of the values of all the records in the specified column name passed to the function.
  2. ROUND Function is used to round the decimal numbers up to mentioned length after the decimal point. Here, 0 is passed because we want integer value (i.e. no number after the decimal point)
    Eg.
    ROUND(2.77, 0) will return 3
    ROUND(2.37, 0) will return 2




Solution-2: Using FLOOR & AVG Function (MySQL Query):

SELECT FLOOR(AVG(POPULATION))
FROM CITY;

NOTE: 
  1. AVG is an aggregation function used to calculate the average of the values of all the records in the specified column name passed to the function.
  2. FLOOR function is used to round down the decimal number to the nearest integer (smaller than or equal to the input number.)
    Eg.
    FLOOR(2.7) will return 2 




Sample Output:

454250

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