Oracle SQL group by rollup and ratio_to_report

Question

I have a table like this

I have a query to show the number of vehicles manufactured in each region and the percentage of vehicles manufactured in the region

 select  
            COALESCE(Region, 'Total') AS Region,
            count(veh_vin) as "Total Vehicles Manufactured",
            round(ratio_to_report(count(veh_vin)) over(),2) as rr
        from( 
            select 
                case 
                    when substr(veh_vin,1,1) between 'A' and 'C' then 'Africa'
                    when substr(veh_vin,1,1) between 'J' and 'R' then 'Asia' 
                    when substr(veh_vin,1,1) between 'S' and 'Z' then 'Europe'
                    when substr(veh_vin,1,1) between '1' and '5' then 'North America'
                    when substr(veh_vin,1,1) between '6' and '7' then 'Oceania'
                    when substr(veh_vin,1,1) between '8' and '9' then 'South America'
                    else 'Unknown'
                end as Region,
                veh_vin
            from vehicle
        )
        group by ROLLUP(Region)
        order by count(veh_vin), Region;

which gives me the following result

But I want something like this, which exclude the total when calculating the percentage.

Is it possible to achieve it with ratio_to_report? If not, how could I alter the query?

Answer 1

I prefer an explicit calculation. You can adjust the calculation (either way) for the aggregated row:

select coalesce(Region, 'Total') AS Region,
       count(*) as "Total Vehicles Manufactured",
       round(count(*) * 1.0 / sum(case when grouping_id(region) = 0 then count(*) end) over (), 2) as rr
from . . .

The same idea doesn't quite work with ratio_to_report() -- because it returns NULL instead of 1. But you could use:

   coalesce(round(ratio_to_report(case when grouping_id(region) = 0 then count(*) end) over(), 2), 1) as rr

Here is a little db<>fiddle.