Leetcode每日一题：197.rising-temperature(上升的温度)

思路：这里主要用到一个日期比较函数DATEDIFF（计算两者的日期差）；

DATEDIFF('2007-12-31','2007-12-30');   # 1
DATEDIFF('2010-12-30','2010-12-31');   # -1

所以查询的条件有两个：

1、与之前的日期相差为 1；
2、比之前的温度高；

SELECT b.Id
FROM Weather as a,Weather as b
WHERE a.Temperature < b.Temperature and DATEDIFF(a.RecordDate,b.RecordDate) = -1;