sqlzoo:SUM and COUNT

梦里梦外; 2022-12-27 01:50 154阅读 0赞

> 1.  Show the total population of the world.

SELECT SUM(population)
    FROM world

> 1.  List all the continents - just once each.

SELECT continent
    FROM world
    GROUP BY continent

SELECT DISTINCT continent
    FROM world

> 1.  Give the total GDP of Africa

SELECT SUM(gdp)
    FROM world
    WHERE continent = 'Africa'

> 1.  How many countries have an area of at least 1000000

SELECT COUNT(*)
    FROM world
    WHERE area >= 1000000

> 1.  What is the total population of (‘Estonia’, ‘Latvia’, ‘Lithuania’)

SELECT SUM(population)
    FROM world
    WHERE name IN('Estonia', 'Latvia', 'Lithuania')

> 1.  For each continent show the continent and number of countries.

SELECT continent, COUNT(*)
    FROM world
    GROUP BY continent

> 1.  For each continent show the continent and number of countries with populations of at least 10 million.

SELECT continent, COUNT(*)
    FROM world
    where population >= 10000000
    GROUP BY continent

> 1.  List the continents that have a total population of at least 100 million.

SELECT continent
    FROM world
    GROUP BY continent
    HAVING SUM(population) >= 100000000

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