Divide the sum of each group by the grand total

Question

I want to get the sum of group A and B separately, and divide each by the total sum.

I tried to use this:

select name, sum(qt)
from ntbl
group by name 

order_id	name	qt
1	A	12
2	A	20
3	B	33
4	B	45

Result should be as:

name	qt	dv
A	32	0.29
B	78	0.70

Answer 1

You can combine aggregate and window functions together:

select name
     , sum(qt) as sum_qt
     , sum(qt) / sum(sum(qt)) over () * 100 as pct_qt
from t
group by name

Answer 2

You can crossjoin another subquery that sums up all quantities

CREATE TABLE ntbl ( `order_id` INTEGER, `name` VARCHAR(1), `qt` INTEGER ); INSERT INTO ntbl (`order_id`, `name`, `qt`) VALUES ('1', 'A', '12'), ('2', 'A', '20'), ('3', 'B', '33'), ('4', 'B', '45');

 SELECT name, sum_name, ROUND(sum_name/sum_qt,2) as dv FROM (select name,SUM(qt) sum_name from ntbl group by name) q1 CROSS JOIN (SELECT SUM(`qt`) sum_qt FROM ntbl) q2

 name | sum_name | dv:--- | -------: |  ---: A |  32 |  0.29 B |  78 |  0.71 

db<>fiddle here