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 | +----+
solution:
Approach 1:
SELECT w1.Id from Weather w1 Inner Join Weather w2 where w1.Date = DATE_ADD(w2.Date, INTERVAL 1 DAY) && w1.Temperature > w2.Temperature
Approach 2:
SELECT w2.Id FROM Weather w1 JOIN Weather w2 ON TO_DAYS(w1.Date) + 1 = TO_DAYS(w2.Date) WHERE w2.Temperature > w1.Temperature;
Optimized Approach 3:
select Id from( select case when Temperature>@pretemp and DATEDIFF(Date,@predate)=1 then Id else null end as Id, @pretemp:=Temperature, @predate:=Date from Weather, (select @pretemp:=null, @predate:=0) init order by Date ) w where w.Id is not null order by Id asc