sqlzoo练习1

开始进行SQL的练习，选择了sqlzoo网站

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表结构

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练习题

主要是练习where语句的使用

-- 1
SELECT population FROM world
WHERE name = 'Germany'
  
-- 2
SELECT name, population FROM world
WHERE name IN ('Sweden', 'Norway','Denmark');

-- 3
SELECT name, area FROM world
WHERE area BETWEEN 200000 AND 250000

quiz

1. 产生下表的结果

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select name, population
from world
wher populantion between 1000000 and 1250000

2. 通配符使用

select name, population
from world 
where name like "AL%"  -- AL开头的名字

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3. Select the code which shows the countries that end in A or L

select name 
from world 
where name like "a%" or name like "%l"

4. 代码运行结果

select name, length(name)
from world 
where length(name)=5 and region="Europe"

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5. 代码运行结果

select name, area*2
from world 
where population = 64000

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6. Select the code that would show the countries with an area larger than 50000 and a population smaller than 10000000

select name, area, population
from world 
where area > 50000 and population < 1000000;

7. Select the code that shows the population density of China, Australia, Nigeria and France

笔记：题目中要求的是人口密度

select name, population / area
from world 
where name in ('China', 'Nigeria', 'France', 'Australia')