问题
给定一个 Weather 表，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。
| 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 |
例如，根据上述给定的 Weather 表格，返回如下 Id:
| Id |
|---|
| 2 |
| 4 |
准备
create database leecote197;
use leecote197;
create table Weather (
Id int(20),
RecordDate date,
Temperature int(20));
insert into Weather values
(1,'2015-01-01',10),
(2,'2015-01-02',25),
(3,'2015-01-03',20),
(4,'2015-01-04',30);
解答
SELECT a.Id
FROM Weather AS a CROSS JOIN Weather AS b
ON DATEDIFF(a.RecordDate, b.RecordDate) = 1
AND a.Temperature > b.Temperature;
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