Presto SQL - distinct in selective group by - presto

Question

ID Name Gender Country
1 Arun Male India
2 Akshay Male England
3 Chethna Female India
4 Priya Female China
5 Piyush Male India
6 Arun Male England
7 Tisha Female England
8 Chethna Female China
I want to group them into male/female first, then the country associated.
Query1 : select Gender, count(distinct name) from Table group by Gender
Output:
Gender count(distinct name)
Male 3
Female 3
Copying the result in JSON like this,
result : {male : {count : 3}, female : {count : 3} }
Query2 : select Gender, Country, count(distinct name) from Table group by Gender, Country
Output:
Gender Country count(distinct name)
Male India 2
Male England 2
Female India 1
Female China 2
Female England 1
Adding this result in the above Json,
result : {Male:{count:3,India:{count:2},England:{count:2}},Female:{count:3,India:{count:1},China:{count:2},England:{count:1}}}
So can I achieve this in a single query?

Answer 1

You can compute the counts by gender and by gender+country in a single query by using GROUPING SETS:
WITH data(id, name, gender, country) AS (
VALUES
(1, 'Arun', 'Male' , 'India'),
(2, 'Akshay', 'Male' , 'England'),
(3, 'Chethna', 'Female', 'India'),
(4, 'Priya', 'Female', 'China'),
(5, 'Piyush', 'Male' , 'India'),
(6, 'Arun', 'Male' , 'England'),
(7, 'Tisha', 'Female', 'England'),
(8, 'Chethna', 'Female', 'China'))
SELECT gender, country, count(distinct name)
FROM data
GROUP BY GROUPING SETS ((gender), (gender, country))
which produces:
gender | country | _col2
--------+---------+-------
Male | England | 2
Female | China | 2
Male | NULL | 3
Female | NULL | 3
Female | India | 1
Male | India | 2
Female | England | 1
(7 rows)