Get Maximum value column from subquery mysql - mysql

Question

i have a mysql query as
SELECT date,shortcode,SUM(count) as myCount
FROM mytable
WHERE smsc='123'
AND username NOT REGEXP '[A-Za-z]+'
AND DATE(date) >= CURDATE() - INTERVAL 7 DAY
GROUP BY shortcode,date
ORDER BY date ASC
Which gives the result as following which is perfectly fine
date
shortcode
myCount
2021-02-18
123
7
2021-02-18
231
15
2021-02-19
783
117
2021-02-19
894
115
2021-02-20
009
70
2021-02-20
565
15
now what i want to do is get max value of maxcount from each day and corresponding shortcode so what i did is
Select date,Max(myCount) as maxim,shortcode
from ( SELECT date,shortcode,SUM(count) as myCount
FROM mytable
WHERE smsc='123'
AND username NOT REGEXP '[A-Za-z]+'
AND DATE(date) >= CURDATE() - INTERVAL 7 DAY
GROUP BY shortcode,date
ORDER BY date ASC ) as a
GROUP BY a.date;
which is not giving me the right result
my desired result is
date | shortcode | maxim
2021-02-18 | 231 |15
2021-02-19 | 783 |117
2020-02-20 | 009 |70

Answer 1

You can use common table expression and row_number() to achieve your desired result:
with cte as (
select date,shortcode,mycount,row_number()over(partition by date order by mycount desc) rn from (SELECT date,shortcode,SUM(count) as myCount
FROM mytable
WHERE smsc='123'
AND username NOT REGEXP '[A-Za-z]+'
AND DATE(date) >= CURDATE() - INTERVAL 7 DAY
GROUP BY shortcode,date )t)
select date,shortcode,mycount from cte where rn=1
This query will generate a sequence for each date orderring by mycount in descendent order. So always the first row for each date will contain the max mycount.

Answer 2

If you can use a variable, the query is:
SET #x='';
SELECT
#x:=date,shortcode,myCount FROM (
SELECT date,shortcode,SUM(count) as myCount
FROM mytable
WHERE smsc='123'
AND username NOT REGEXP '[A-Za-z]+'
AND DATE(date) >= CURDATE() - INTERVAL 7 DAY
GROUP BY shortcode,date
ORDER BY date ASC,myCount DESC
) a
WHERE #x<>date
;
Fiddle