Description：Given a Weather table, write a SQL query to find all dates‘ Ids with higher temperature compared to its previous (yesterday‘s) dates.
选出比前一天温度高的Id
使用自连接，to_days函数是返回从零年开始的总天数。
（为何把=误写成<会Runtime Error啊 不应该是WrongAnser！）
# Write your MySQL query statement below select w2.Id from Weather w1, Weather w2 where to_days(w1.Date)+1=to_days(w2.Date) and w1.Temperature<w2.Temperature;
原文：http://www.cnblogs.com/wxisme/p/4440332.html