Problem Statement
Given two tables, City and Country whose descriptions are given below. Find the sum of population of all the Cities that lies in “Asia” continent.
City
+-------------+----------+
| Field | Type |
+-------------+----------+
| ID | int(11) |
| Name | char(35) |
| CountryCode | char(3) |
| District | char(20) |
| Population | int(11) |
+-------------+----------+
Country
+----------------+-------------+
| Field | Type |
+----------------+-------------+
| Code | char(3) |
| Name | char(52) |
| Continent | char(50) |
| Region | char(26) |
| SurfaceArea | float(10,2) |
| IndepYear | smallint(6) |
| Population | int(11) |
| LifeExpectancy | float(3,1) |
| GNP | float(10,2) |
| GNPOld | float(10,2) |
| LocalName | char(45) |
| GovernmentForm | char(45) |
| HeadOfState | char(60) |
| Capital | int(11) |
| Code2 | char(2) |
+----------------+-------------+
PS: City.CountryCode and Country.Code is same key.
Solution
Select sum(City.Population) from City Inner Join Country ON City.CountryCode = Country.Code and Continent='Asia';