【Leetcode】197. Rising Temperature

難度：Easy

id is the column with unique values for this table.

There are no different rows with the same recordDate.

This table contains information about the temperature on a certain day.

原文：

Write a solution to find all dates' id with higher temperatures compared to its previous dates (yesterday).

Return the result table in any order.

The result format is in the following example.

個人翻譯（非逐字翻譯）：

編寫一個解決方案，尋找與之前的日期（昨天），相比之下溫度更高的日期，

以不排序的方式回傳結果。

輸入：

輸出：

註釋：

In 2015-01-02, the temperature was higher than the previous day (10 -> 25).

In 2015-01-04, the temperature was higher than the previous day (20 -> 30).

個人理解

前面遇到的Join語法都是兩個表格合一，這個看來是做交叉連接，有些解答甚至連join語法不會用到。但基於理解、練習join語法的情況下，目前選擇使用下列方式。

而本次習題先整合表格的資料，讓系統列出後再用datediff()來處理兩個時間的間隔、後一天比前一天溫度高的狀態來輸出成結果。

程式碼

select w2.id

from Weather w1

join Weather w2

on datediff(w2.recordDate, w1.recordDate) = 1 and w2.temperature > w1.temperature;

或

select today.id

from Weather yesterday

cross join Weather today

where datediff(today.recordDate,yesterday.recordDate)=1

and today.temperature>yesterday.temperature;

小屋創作