LeetCode MySQL-197. Rising Temperature

    AllenLi
    LeetCode MySQL

    Write an SQL query to find all dates’ Id with higher temperatures compared to its previous dates (yesterday).
    Return the result table in any order.

    寫一個 SQL Query來尋找比昨日溫度高的所有ID。
可任意排序結果。

    Table: Weather

    +---------------+---------+
| Column Name   | Type    |
+---------------+---------+
| id            | int     |
| recordDate    | date    |
| temperature   | int     |
+---------------+---------+
id is the primary key for this table.
This table contains information about the temperature on a certain day.

    Example 1:

    Input: 
Weather table:
+----+------------+-------------+
| id | recordDate | temperature |
+----+------------+-------------+
| 1  | 2015-01-01 | 10          |
| 2  | 2015-01-02 | 25          |
| 3  | 2015-01-03 | 20          |
| 4  | 2015-01-04 | 30          |
+----+------------+-------------+
Output: 
+----+
| id |
+----+
| 2  |
| 4  |
+----+
Explanation: 
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).

    Solution:
    1. 選擇標題 Weather 中的 id。
    2. 假設有兩個相同的 Weather 表。
    3. 當第一張表的溫度大於第二張表時，且日期相差一天。

    Code1:

    SELECT w1.id 
	FROM Weather AS w1, Weather AS w2
WHERE w1.temperature > w2.temperature 
  AND DATEDIFF(w1.recordDate, w2.recordDate) = 1;

    newWeather

    DATEDIFF():

    DATEDIFF(datepart,startdate,enddate)

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