SQL bucket based on totals

Question

I have a list of retailers and their total sales. I want to bucket them in 4 categories based on their total sales. I want to show 10% of retailers cover 70% of sales.

In the example below, I am trying to divide the retailers in 4 quantiles. In the below case total sales for all 10 retailers is 4500. In order to divide these retailers in 4 quantiles, I have sorted data by sales from high to low and assign them quantile.

Sum of sales for retailers in each quantile is around 4500/4= 1100.

How can I replicate this logic in sql?

Here's sample data :-

Answer 1

If I understand correctly, you can use cumulative sums and some arithmetic. I think this does what you want.

select t.*,
       ceiling(running_total * 4.0 / total_total)
from (select t.*, sum(total) over (order by total desc) as running_total,
             sum(total) over() as total_total
      from t
     ) t