I am not so into database and I have the following problem implementing a query. I am using MySql
I have a MeteoForecast table like this:
CREATE TABLE MeteoForecast (
id BigInt(20) NOT NULL AUTO_INCREMENT,
localization_id BigInt(20) NOT NULL,
seasonal_forecast_id BigInt(20),
meteo_warning_id BigInt(20),
start_date DateTime NOT NULL,
end_date DateTime NOT NULL,
min_temp Float,
max_temp Float,
icon_link VarChar(255) CHARACTER SET latin1 COLLATE latin1_swedish_ci NOT NULL,
PRIMARY KEY (
id
)
) ENGINE=InnoDB AUTO_INCREMENT=3 ROW_FORMAT=DYNAMIC DEFAULT CHARACTER SET latin1 COLLATE latin1_swedish_ci;
It contains meteo forecast information, something like this:
id localization_id start_date end_date min_temp max_temp icon_link
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1 1 18/09/2017 06:00:00 18/09/2017 12:00:00 15 24 Mostly_Cloudy_Icon.png
2 1 18/09/2017 12:00:00 18/09/2017 18:00:00 15 24 Light_Rain.png
3 1 19/09/2017 06:00:00 19/09/2017 12:00:00 12 22 Mostly_Cloudy_Icon.png
4 1 19/09/2017 12:00:00 19/09/2017 18:00:00 13 16 Mostly_Cloudy_Icon.png
5 1 20/09/2017 06:00:00 20/09/2017 12:00:00 18 26 Light_Rain.png
6 1 20/09/2017 12:00:00 20/09/2017 18:00:00 17 25 Light_Rain.png
So, as you can see in the previous dataset, each record have a starting datetime and and ending datetime. This because I am collecting more forecast information in a specific day (it is based on time range, in the example for each day a record from 06:00 am to 12:00 and another record from 12:00 to 18:00 pm).
So, I created this simple query that extracts all the records in a specific range (in this case 2 days):
select * from MeteoForecast
where start_date between '2017-09-18 06:00:00' and '2017-09-20 06:00:00'
order by start_date desc;
I have to modify this query in the following way:
For each record retrieved by the previous query have to be added a new field named global_max_temp that is the maximum value of the max_temp field in the same day.
Doing an example related to the records related to theday having start_date value equal to 19/09/2017..., these are the records that I need to obtain:
id localization_id start_date end_date min_temp max_temp icon_link global_max_temp
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
3 1 19/09/2017 06:00:00 19/09/2017 12:00:00 12 22 Mostly_Cloudy_Icon.png 22
4 1 19/09/2017 12:00:00 19/09/2017 18:00:00 13 16 Mostly_Cloudy_Icon.png 22
As you can see here the last field (inserted manually in this mock) is global_max_temp and in both records related to this day contains the value 22 because it is the maximum value of the max_temp field of all the records related to a specific day.
This is the query calculating these global_max_temp value:
select max(max_temp) from MeteoForecast
where start_date = '2017-09-19 06:00:00'
How can I add this feature to my original query?
Can you try something like this:
SELECT A.*, B.GLOBAL_MAX_TEMP
FROM (
select id, start_date, end_date, min_temp, max_temp
from MeteoForecast
where start_date between '2017-09-18 06:00:00' and '2017-09-20 06:00:00'
) A
INNER JOIN (SELECT date(start_date) AS date_only, MAX(max_temp) AS GLOBAL_MAX_TEMP
FROM MeteoForecast
WHERE start_date BETWEEN '2017-09-18 06:00:00' and '2017-09-20 06:00:00'
GROUP BY date(start_date)
) B ON date(A.start_date) = B.date_only
ORDER by start_date desc;