leetcode197-Rising Temperature

问题描述：

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 | +----+

找出温度比昨天高的那一天对应的ID。

问题求解：

1、where

select w1.Id from Weather w1, Weather w2 where TO_DAYS(w1.Date)=TO_DAYS(w2.Date)+1 and w1.Temperature>w2.Temperature;

2、inner join … on

select w1.Id from Weather w1 inner join Weather w2 on TO_DAYS(w1.Date)=TO_DAYS(w2.Date)+1 and w1.Temperature>w2.Temperature;