Rising Temperature SQL Challenge - MySQL Solution

1. Introduction

In this blog post, we're going to delve into a MySQL solution for identifying dates with rising temperatures compared to the previous day. This is a common scenario in weather data analysis.

Problem

The challenge is to write a MySQL query that finds all dates with higher temperatures compared to their previous dates in the Weather table.

Database Table:

Weather Table:

id	recordDate	temperature
1	2015-01-01	10
2	2015-01-02	25

3. MySQL Solution

SELECT a.id
FROM Weather a
JOIN Weather b ON a.recordDate = b.recordDate + INTERVAL 1 DAY
WHERE a.temperature > b.temperature;

Output:

id
2

Explanation:

1. The query performs a self-join on the Weather table.

2. It joins each record (aliased as a) with its previous day's record (aliased as b) based on the recordDate.

3. The join condition checks that a's recordDate is exactly one day ahead of b's recordDate.

4. The WHERE clause filters for those records where a's temperature is greater than b's temperature, effectively identifying days with rising temperatures compared to the previous day.