SQL條件語法 列出大型國家 Leetcode #595

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題目敘述

題目會給我們一張World資料表，裡面分別有name、 continent、area、population 、gdp等欄位，其中name 是主鍵Primary Key。

輸出的順序不拘。

Table: World

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| name        | varchar |
| continent   | varchar |
| area        | int     |
| population  | int     |
| gdp         | bigint  |
+-------------+---------+
name is the primary key (column with unique values) 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.

詳細的題目可在這裡看到

測試範例

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

約束條件

大型國家的定義是人口大於等於兩千五百萬人 或者 土地面積大於等於三百萬平方公里。

演算法

也是基本的入門題，在基本的查詢語法上，加上條件判斷 OR 表達兩個條件取其一滿足的意思，去篩選結果即可。

SELECT ...欄位 FROM ...表格 WHERE ...條件1 OR 條件2

如果是第一次接觸SQL的同學，請到這邊學習基本的SQL 語法。

程式碼

SELECT name, population, area
FROM world
WHERE population >= 25000000 OR area >= 3000000;

關鍵知識點

掌握基本的SELECT ...欄位 FROM ...表格 WHERE ...條件1 OR 條件2

SQL語法即可。

Reference:

[1] MySQL sol. based on select ... from ...where condition - Big Countries - LeetCode