select
    invoice.billing_country as country,
    count(distinct invoice.invoice_id) as total_invoice,
    count(distinct client.customer_id) as total_customer
from invoice as invoice
join client as client
    on client.customer_id = invoice.customer_id
where 1=1
    and extract(year from cast(invoice_date as date)) = (
        select
            extract(year from cast(invoice_date as date)) as year
        from invoice
        where 1=1
            and extract(month from cast(invoice_date as date)) in (6,7,8)
        group by extract(year from cast(invoice_date as date))
        order by sum(total) desc
        limit 1
)
group by  1
order by 2 desc, 1