表 Weather
+---------------+---------+ | Column Name | Type | +---------------+---------+ | id | int | | recordDate | date | | temperature | int | +---------------+---------+ id 是这个表的主键 该表包含特定日期的温度信息
编写一个 SQL 查询,来查找与之前(昨天的)日期相比温度更高的所有日期的 id 。返回结果 不要求顺序 。
查询结果格式如下例:
Weather +----+------------+-------------+ | id | recordDate | Temperature | +----+------------+-------------+ | 1 | 2015-01-01 | 10 | | 2 | 2015-01-02 | 25 | | 3 | 2015-01-03 | 20 | | 4 | 2015-01-04 | 30 | +----+------------+-------------+
Result table: +----+ | id | +----+ | 2 | | 4 | +----+ 2015-01-02 的温度比前一天高(10 -> 25) 2015-01-04 的温度比前一天高(30 -> 20)
Write an SQL query to find all dates' id with higher temperature compared to its previous dates (yesterday). Return the result table in any order.
分析:相邻两天日期的比较,Mysql内置函数中考虑使用:
1、TO_DAYS(date);
2、DATE_SUB(date,INTERVAL expr type) ;
3、DATEDIFF(date1,date2);
# TO_DAYS(date) 返回从0年以来的天数 # DATEDIFF(b.recordDate,a.recordDate)=1 返回两个日期间隔的天数 # DATE_SUB(b.recordDate,INTERVAL 1 DAY) 返回两个日期间隔的天数 select b.id from Weather a,Weather b where TO_DAYS(a.recordDate) = TO_DAYS(b.recordDate)-1 and b.Temperature > a.Temperature #where a.recordDate = DATE_SUB(b.recordDate,INTERVAL 1 DAY) and b.Temperature > a.Temperature #where DATEDIFF(b.recordDate,a.recordDate)=1 and b.Temperature > a.Temperature
