I'm trying to calculate the percentage of a customer has spent over the total sales value.
I have calculated the total sales value per customer using sum() and group by, but after I use group by, I cannot differentiate the total sales value and the individual total for each sustomer.
is there anyway i could get around this?
i got to here so far and dont know what to do next:
select c.firstname ||' '|| c.lastname as 'Ful name',
sum(total) as 'Sales value',
/*something to calculate percentage*/,
from invoice i inner join customer c on i.customerid = c.customerid
group by i.customerid order by sum(total) desc limit 5;