select all rows based on max(cases) and min(date) - sql

Question

I have a table covid, my table looks something like this:
location | date | new_cases | total_deaths | new_deaths
----------------------------------------------------------------
Afghanistan 2020-04-07 38 7 0
Afghanistan 2020-04-08 30 11 4
Afghanistan 2020-04-09 56 14 3
Afghanistan 2020-04-10 61 15 1
Afghanistan 2020-04-11 37 15 0
Afghanistan 2020-04-12 34 18 3
In this case, I want to get rows location based on max(new_cases),this is my query:
select a.*
from covid a
join (
select location, max(new_cases) highest_case
from covid
group by location
) b
on a.location = b.location
and a.new_cases = b.highest_case
but I found the same location and max(case) values with the different date value, this is the result.
location | date | new_cases | total_deaths | new_deaths
----------------------------------------------------------------
Bhutan 2020-06-08 11 0 0
Bolivia 2020-07-28 2382 2647 64
Bonaire Sint 2020-04-02 2 0 0
Bonaire Sint 2020-07-15 2 0 0
Botswana 2020-07-24 164 1 0
Now, how can I get the values based on min(date), please give me advice for fix this, and the output should be like this:
location | date | new_cases | total_deaths | new_deaths
----------------------------------------------------------------
Bhutan 2020-06-08 11 0 0
Bolivia 2020-07-28 2382 2647 64
Bonaire Sint 2020-04-02 2 0 0
Botswana 2020-07-24 164 1 0

Answer 1

Use distinct on:
select distinct on (location) c.*
from covid c
order by location, new_cases desc;
For the minimum date, use:
order by location, date asc;

Answer 2

You can use window function Max() to get max_cases (according to location) and then numbering rows (to fetch the min date) :
select location,date,new_cases,total_deaths,new_deaths from
(
--get min date with max_cases
select row_number()over(partition by location order by date)n,date,
location,new_cases,total_deaths,new_deaths
from
(
select location,date,max(new_cases)over(partition by
location)max_case,new_cases,total_deaths,new_deaths from covid --get max_case
) X
where new_cases=max_case --fetch only max case
)Y where n=1