SQL Coding Exercise – Rising Temperature

Given a Weather table, 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 |
+----+

The SQL puzzle is classified as ‘Easy’ in Oj Online Judge: https://leetcode.com/problems/rising-temperature/

The solution is to select from the table two times and compare the dates and temperature:

select A.Id from Weather as A, Weather as B 
where A.Temperature > B.Temperature and TO_DAYS(A.Date) = TO_DAYS(B.Date) + 1

Of course, you could also use “INTERVAL 1 DAY” to accomplish the same task.

select A.Id from Weather as A, Weather as B 
where A.Temperature > B.Temperature and A.Date = B.Date + INTERVAL 1 DAY

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