595. Big Countries

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      |+--------------+-------------+--------------+

Answer：

SELECT name,population,area FROM world where area > 3000000 or population > 25000000

出于效率考虑 最好将以上sql语句改为以下
SELECT name,population,area FROM world where area > 3000000 UNION SELECT name,population,area FROM world where population > 25000000 

思路：刚刚开始刷leetcode的题目，选择了从easy开始，这题就是简单的sql语句，之前了解过如何优化SQL，所以选择了用union代替了or