Rising Temperature

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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) | RecordDate(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 |
+----+

---

解题思路：

自己连接自己，条件是连接自己昨天的行。

TO_DAYS函数 返回一个天数! 啊哈？什么天数? 从年份0开始的天数 

比如：

mysql> SELECT TO_DAYS(‘1997-10-07′); 

结果  729669
就是从0年开始 到1997年10月7号之间的天数

理解这个之后那么一切就变得拉么简单！有一张表！lito表 有一个字段 create_time  类型 datetime  

如果要查询当前表中昨天的数据那么

select * from lito where to_days(now())-to_days(create_time)<1

select w.Id from Weather as w 
join Weather as preW on TO_DAYS(w.RecordDate)=1+TO_DAYS(preW.RecordDate)
where w.Temperature > preW.Temperature;