LeetCode_197. Rising Temperature

197. Rising Temperature

Given a Weather table, write a SQL query to find all dates’ Ids with higher temperature compared to its previous (yesterday’s) dates.

+———+————+——————+
| Id(INT) | Date(DATE) | Temperature(INT) |
+———+————+——————+
| 1 | 2015-01-01 | 10 |
| 2 | 2015-01-02 | 25 |
| 3 | 2015-01-03 | 20 |
| 4 | 2015-01-04 | 30 |
+———+————+——————+

For example, return the following Ids for the above Weather table:

+—-+
| Id |
+—-+
| 2 |
| 4 |
+—-+

解答：找出温度升高那天的Id，题目比较简单，关键是如何找出连续的两天,需要借助MySQL内置的天数转换函数(DATADIFF/TODAYS)：

# Write your MySQL query statement below
SELECT W1.Id FROM Weather AS W1, Weather AS W2
WHERE W1.Temperature > W2.Temperature AND DATEDIFF(W1.Date, W2.Date) = 1;