LeetCode:595 Big Countions-优快云博客

本文介绍了一个具体的SQL查询案例，目标是从包含国家基本信息的World表中筛选出面积超过3百万平方公里或人口超过2500万的大国，并展示了如何通过简单的SQL语句实现这一需求。

一：题目

There is a table World

+-----------------+------------+------------+--------------+---------------+
| name            | continent  | area       | population   | gdp           |
+-----------------+------------+------------+--------------+---------------+
| Afghanistan     | Asia       | 652230     | 25500100     | 20343000      |
| Albania         | Europe     | 28748      | 2831741      | 12960000      |
| Algeria         | Africa     | 2381741    | 37100000     | 188681000     |
| Andorra         | Europe     | 468        | 78115        | 3712000       |
| Angola          | Africa     | 1246700    | 20609294     | 100990000     |
+-----------------+------------+------------+--------------+---------------+

A country is big if it has an area of bigger than 3 million square km or a population of more than 25 million.

Write a SQL solution to output big countries' name, population and area.

For example, according to the above table, we should output:

+--------------+-------------+--------------+
| name         | population  | area         |
+--------------+-------------+--------------+
| Afghanistan  | 25500100    | 652230       |
| Algeria      | 37100000    | 2381741      |
+--------------+-------------+--------------+

二：题意解读

大意就是从表格中选出符合条件的国家，也就是领土大于3 million square km或者人口大于25 million。

三：基本思路

这是数据库方面的题目，第一步可以设定查询条件，按照题目意思是二选一的条件，那么该如何作答就显而易见了。

四：代码

SELECT name, area, population

FROM World

WHERE World.area > 3000000

OR World.population > 25000000;