題目敘述
SQL Schema >
Create table If Not Exists World (name varchar(255), continent varchar(255), area int, population int, gdp int)
Truncate table World
insert into World (name, continent, area, population, gdp) values ('Afghanistan', 'Asia', '652230', '25500100', '20343000000')
insert into World (name, continent, area, population, gdp) values ('Albania', 'Europe', '28748', '2831741', '12960000000')
insert into World (name, continent, area, population, gdp) values ('Algeria', 'Africa', '2381741', '37100000', '188681000000')
insert into World (name, continent, area, population, gdp) values ('Andorra', 'Europe', '468', '78115', '3712000000')
insert into World (name, continent, area, population, gdp) values ('Angola', 'Africa', '1246700', '20609294', '100990000000')
Table: World
+-------------+---------+
| Column Name | Type |
+-------------+---------+
| name | varchar |
| continent | varchar |
| area | int |
| population | int |
| gdp | int |
+-------------+---------+
name is the primary key column for this table.
Each row of this table gives information about the name of a country, the continent to which it belongs, its area, the population, and its GDP value.
A country is big if:
- it has an area of at least three million (i.e.,
3000000 km2), or
- it has a population of at least twenty-five million (i.e.,
25000000).
Write an SQL query to report the name, population, and area of the big countries.
Return the result table in any order.
The query result format is in the following example.
Example 1:
Input:
World table:
+-------------+-----------+---------+------------+--------------+
| name | continent | area | population | gdp |
+-------------+-----------+---------+------------+--------------+
| Afghanistan | Asia | 652230 | 25500100 | 20343000000 |
| Albania | Europe | 28748 | 2831741 | 12960000000 |
| Algeria | Africa | 2381741 | 37100000 | 188681000000 |
| Andorra | Europe | 468 | 78115 | 3712000000 |
| Angola | Africa | 1246700 | 20609294 | 100990000000 |
+-------------+-----------+---------+------------+--------------+
Output:
+-------------+------------+---------+
| name | population | area |
+-------------+------------+---------+
| Afghanistan | 25500100 | 652230 |
| Algeria | 37100000 | 2381741 |
+-------------+------------+---------+
題目翻譯
從資料表 World 找出大城市並回傳其 name, population, area，並且不須排序。而大城市的定義是：
- 區域面積至少 3,000,000
- 人口數至少 25,000,000
解法解析
解法範例
SQL
SELECT name,
population,
area
FROM `World`
WHERE area >= 3000000
OR population >= 25000000;
第二種寫法沒有特別的必要，只是寫來表示也是有這種寫法，就是用 UNION 來連結兩個 Query。
SELECT name,
population,
area
FROM `World`
WHERE area >= 3000000
UNION
SELECT name,
population,
area
FROM `World`
WHERE population >= 25000000;