Population Census Solution
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Problem
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:
Field | Type |
---|---|
ID | NUMBER |
NAME | VARCHAR2(17) |
COUNTRYCODE | VARCHAR2(3) |
DISTRICT | VARCHAR2(20) |
POPULATION | NUMBER |
Field | Type |
---|---|
CODE | VARCHAR2(3) |
NAME | VARCHAR2(44) |
CONTINENT | VARCHAR2(13) |
REGION | VARCHAR2(25) |
SURFACEAREA | NUMBER |
INDEPYEAR | VARCHAR2(5) |
POPULATION | NUMBER |
LIFEEXPECTANCY | VARCHAR2(4) |
GNP | NUMBER |
GNPOLD | VARCHAR2(9) |
LOCALNAME | VARCHAR2(44) |
GOVERNMENTFORM | VARCHAR2(44) |
HEADOFSTATE | VARCHAR2(32) |
CAPITAL | VARCHAR2(4) |
CODE2 | VARCHAR2(2) |
Solution – Population Census
MySQL Code
select sum(city.population) from country left join city on country.code = city.countrycode where country.continent = 'Asia'
A population census is an enumeration of people, houses, firms, or other important items in a country or region at a particular time. It is used to collect demographic, economic, and social data pertaining to a specific time for all persons in a country or fixed or defined area part of a country¹.
The modern idea of a population census as a complete enumeration of all the people and their important characteristics for purposes of understanding the basic structure and trends of the society rather than for identifying and controlling particular individuals slowly arose in the 17th and 18th centuries.
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