197_Rising Temperature

Given aWeathertable, write a SQL query to find all dates' Ids with higher temperature compared to its previous (yesterday's) dates.

+---------+------------+------------------+
| Id(INT) | Date(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 |
+----+

Solution

Use DATEDIFF() function to only inner join yesterday's temperature.

SELECT w1.Id AS Id
FROM Weather AS w1 INNER JOIN Weather AS w2
ON DATEDIFF(w1.Date, w2.Date) = 1
WHERE w1.Temperature > w2.Temperature;