sql notes: hackerrank revising aggregations

Problem

Query the total population of all cities in CITY where District is California.

Input Format
The CITY table is described as follows:

Analysis

• query total population ==> SELECT SUM(POPULATION)
• in CITY table ==> FROM CITY
• District is California ==> WHERE DISTRICT = ‘California’

Solution

1

SELECT SUM(POPULATION) FROM CITY WHERE DISTRICT = 'California';

Link

Revising Aggregations - The Sum Function
(中文版) SQL 笔记: Hackerrank Revising Aggregations - The Sum Function